Prepare 0.10.0-beta.2

* Implement CustomizeConnection::on_release() for SmtpConnection

.appveyor.yml

@@ -1,14 +0,0 @@
-environment:
-  matrix:
-    - TARGET: x86_64-pc-windows-msvc
-install:
-  - curl -sSf -o rustup-init.exe https://win.rustup.rs/
-  - rustup-init.exe -y --default-host %TARGET%
-  - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
-  - rustc -vV
-  - cargo -vV
-build: false
-test_script:
-  - cargo build --verbose --manifest-path lettre/Cargo.toml
-  - cargo test --verbose --manifest-path lettre_email/Cargo.toml
-  

.build-scripts/codecov.sh

@@ -1,20 +0,0 @@
-#!/bin/bash
-
-set -xe
-
-wget https://github.com/SimonKagstrom/kcov/archive/master.tar.gz
-tar xzf master.tar.gz
-cd kcov-master
-mkdir build
-cd build
-cmake ..
-make
-make install DESTDIR=../../kcov-build
-cd ../..
-rm -rf kcov-master
-for file in target/debug/lettre*[^\.d]; do
-  mkdir -p "target/cov/$(basename $file)"
-  ./kcov-build/usr/local/bin/kcov --exclude-pattern=/.cargo,/usr/lib --verify "target/cov/$(basename $file)" "$file"
-done
-bash <(curl -s https://codecov.io/bash)
-echo "Uploaded code coverage"

.build-scripts/site-upload.sh

@@ -1,10 +0,0 @@
-#!/bin/bash
-
-set -xe
-
-cd website
-make clean && make
-echo "lettre.at" > _book/CNAME
-sudo pip install ghp-import
-ghp-import -n _book
-git push -f https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git gh-pages

.github/FUNDING.yml

@@ -0,0 +1 @@
+liberapay: amousset

.github/workflows/audit.yml

@@ -0,0 +1,12 @@
+name: Security audit
+on:
+  schedule:
+    - cron: '0 0 * * *'
+jobs:
+  audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/audit-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/test.yml

@@ -0,0 +1,144 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+env:
+  RUST_BACKTRACE: full
+
+jobs:
+  rustfmt:
+    name: rustfmt / stable
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Install rust
+        run: |
+          rustup update --no-self-update stable
+          rustup component add rustfmt
+
+      - name: cargo fmt
+        run: cargo fmt --all -- --check
+
+  clippy:
+    name: clippy / stable
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Install rust
+        run: |
+          rustup update --no-self-update stable
+          rustup component add clippy
+
+      - name: Run clippy
+        run: cargo clippy --all-features --all-targets -- -D warnings
+
+  check:
+    name: check / stable
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup cache
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-check
+
+      - name: Install rust
+        run: rustup update --no-self-update stable
+      
+      - name: Install cargo hack
+        run: cargo install cargo-hack --debug
+
+      - name: Check with cargo hack
+        run: cargo hack check --feature-powerset --depth 3
+
+  test:
+    name: test / ${{ matrix.name }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        include:
+          - name: stable
+            rust: stable
+          - name: beta
+            rust: beta
+          - name: 1.45.2
+            rust: 1.45.2
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup cache
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-test-${{ matrix.rust }}
+
+      - name: Install rust
+        run: |
+          rustup default ${{ matrix.rust }}
+          rustup update --no-self-update ${{ matrix.rust }}
+
+      - name: Install postfix  
+        run: |
+          DEBIAN_FRONTEND=noninteractive sudo apt-get update
+          DEBIAN_FRONTEND=noninteractive sudo apt-get -y install postfix
+
+      - name: Run SMTP server
+        run: smtp-sink 2525 1000&
+
+      - name: Test with no default features
+        run: cargo test --no-default-features
+
+      - name: Test with default features
+        run: cargo test
+
+      - name: Test with all features
+        run: cargo test --all-features
+  
+#  coverage:
+#    name: Coverage
+#    runs-on: ubuntu-latest
+#    steps:
+#      - uses: actions/checkout@v2
+#      - uses: actions-rs/toolchain@v1
+#        with:
+#          toolchain: nightly
+#          override: true
+#      - run: sudo DEBIAN_FRONTEND=noninteractive apt-get -y install postfix
+#      - run: smtp-sink 2525 1000&
+#      - uses: actions-rs/cargo@v1
+#        with:
+#          command: test
+#          args: --no-fail-fast
+#        env:
+#          CARGO_INCREMENTAL: "0"
+#          RUSTFLAGS: "-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Zno-landing-pads"
+#      - id: coverage
+#        uses: actions-rs/grcov@v0.1
+#      - name: Coveralls upload
+#        uses: coverallsapp/github-action@master
+#        with:
+#          github-token: ${{ secrets.GITHUB_TOKEN }}
+#          path-to-lcov: ${{ steps.coverage.outputs.report }}

.gitignore

@@ -1,6 +1,7 @@
 .vscode/
 .project/
 .idea/
+lettre.sublime-*
 lettre.iml
 target/
 /Cargo.lock

.travis.yml

@@ -1,31 +0,0 @@
-language: rust
-rust:
-- stable
-- beta
-- nightly
-- 1.26.0
-matrix:
-  allow_failures:
-  - rust: nightly
-sudo: required
-addons:
-  apt:
-    packages:
-    - postfix
-    - libcurl4-openssl-dev
-    - libelf-dev
-    - libdw-dev
-    - cmake
-    - gcc
-    - binutils-dev
-    - libiberty-dev
-    - npm
-before_script:
-- smtp-sink 2525 1000&
-- sudo chgrp -R postdrop /var/spool/postfix/maildrop
-- sudo npm set strict-ssl false && sudo npm install -g gitbook-cli
-script:
-- cargo test --verbose --all --all-features
-after_success:
-- ./.build-scripts/codecov.sh
-- '[ "$TRAVIS_BRANCH" = "v0.9.x" ] && [ $TRAVIS_PULL_REQUEST = false ] && ./.build-scripts/site-upload.sh'

CHANGELOG.md

@@ -1,3 +1,76 @@
+<a name="v0.10.0"></a>
+### v0.10.0 (unreleased)
+
+#### Upgrade notes
+
+Several breaking changes were made between 0.9 and 0.10, but changes should be straightforward:
+
+* MSRV is now 1.45.2
+* The `lettre_email` crate has been merged into `lettre`. To migrate, replace `lettre_email` with `lettre::message`
+  and make sure to enable the `builder` feature (it's enabled by default).
+* `SendableEmail` has been renamed to `Email` and `EmailBuilder::build()` produces it directly. To migrate,
+  rename `SendableEmail` to `Email`.
+* The `serde-impls` feature has been renamed to `serde`. To migrate, rename the feature.
+
+#### Features
+
+* Add `tokio` 0.2 and 1.0 support
+* Add `rustls` support
+* Add `async-std` support. NOTE: native-tls isn't supported when using async-std for the smtp transport.
+* Allow enabling multiple SMTP authentication mechanisms
+* Allow providing a custom message id
+* Allow sending raw emails
+
+#### Breaking Changes
+
+* Merge `lettre_email` into `lettre`
+* Merge `Email` and `SendableEmail` into `lettre::message::Email`
+* SmtpTransport is now an high level SMTP client. It provides connection pooling and shortcuts for building clients using commonly desired values
+* Refactor `TlsParameters` implementation to not expose the internal TLS library
+* `FileTransport` writes emails into `.eml` instead of `.json`
+* When the hostname feature is disabled or hostname cannot be fetched, `127.0.0.1` is used instead of `localhost` as EHLO parameter (for better RFC compliance and mail server compatibility)
+* The `new` method of `ClientId` is deprecated
+* Rename `serde-impls` feature to `serde`
+
+
+#### Bug Fixes
+
+* Fix argument injection in `SendmailTransport` (see [RUSTSEC-2020-0069](https://github.com/RustSec/advisory-db/blob/master/crates/lettre/RUSTSEC-2020-0069.md))
+* Correctly encode header values containing non-ASCII characters
+* Timeout bug causing infinite hang
+* Fix doc tests in website
+* Fix docs for `domain` field
+
+#### Misc
+
+* Improve documentation, examples and tests
+* Replace `line-wrap`, `email`, `bufstream` with our own implementations
+* Remove `bytes`
+* Remove `time`
+* Remove `fast_chemail`
+* Update `base64` to 0.13
+* Update `hostname` to 0.3
+* Update to `nom` 6
+* Replace `log` with `tracing`
+* Move CI to Github Actions
+* Use criterion for benchmarks
+
+<a name="v0.9.2"></a>
+### v0.9.2 (2019-06-11)
+
+#### Bug Fixes
+
+* **email:**
+  * Fix compilation with Rust 1.36+ ([393ef8d](https://github.com/lettre/lettre/commit/393ef8dcd1b1c6a6119d0666d5f09b12f50f6b4b))
+
+<a name="v0.9.1"></a>
+### v0.9.1 (2019-05-05)
+
+#### Features
+
+* **email:**
+  * Re-export mime crate ([a0c8fb9](https://github.com/lettre/lettre/commit/a0c8fb9))
+
 <a name="v0.9.0"></a>
 ### v0.9.0 (2019-03-17)
 

CODE_OF_CONDUCT.md

@@ -34,13 +34,13 @@ This Code of Conduct applies both within project spaces and in public spaces whe
 
 ## Enforcement
 
-Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by contacting the project team at contact@lettre.at. The project team will review and investigate all complaints, and will respond in a way that it deems appropriate to the circumstances. The project team is obligated to maintain confidentiality with regard to the reporter of an incident. Further details of specific enforcement policies may be posted separately.
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by contacting the project team at contact@lettre.rs. The project team will review and investigate all complaints, and will respond in a way that it deems appropriate to the circumstances. The project team is obligated to maintain confidentiality with regard to the reporter of an incident. Further details of specific enforcement policies may be posted separately.
 
 Project maintainers who do not follow or enforce the Code of Conduct in good faith may face temporary or permanent repercussions as determined by other members of the project's leadership.
 
 ## Attribution
 
-This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4, available at [http://contributor-covenant.org/version/1/4][version]
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4, available at [https://www.contributor-covenant.org/version/1/4][version]
 
-[homepage]: http://contributor-covenant.org
-[version]: http://contributor-covenant.org/version/1/4/
+[homepage]: https://www.contributor-covenant.org
+[version]: https://www.contributor-covenant.org/version/1/4/

CONTRIBUTING.md

@@ -33,3 +33,11 @@ Any line of the commit message cannot be longer 72 characters.
     all
 
 The body explains the change, and the footer contains relevant changelog notes and references to fixed issues.
+
+### Release process
+
+Releases are made using `cargo-release`:
+
+```bash
+cargo release --dry-run 0.10.0 --prev-tag-name v0.9.2 -v
+```

Cargo.toml

@@ -1,5 +1,155 @@
-[workspace]
-members = [
-    "lettre",
-    "lettre_email",
-]
+[package]
+name = "lettre"
+# remember to update html_root_url and README.md (Cargo.toml example and deps.rs badge)
+version = "0.10.0-beta.2"
+description = "Email client"
+readme = "README.md"
+homepage = "https://lettre.rs"
+repository = "https://github.com/lettre/lettre"
+license = "MIT"
+authors = ["Alexis Mousset <contact@amousset.me>", "Paolo Barbolini <paolo@paolo565.org>"]
+categories = ["email", "network-programming"]
+keywords = ["email", "smtp", "mailer", "message", "sendmail"]
+edition = "2018"
+
+[badges]
+is-it-maintained-issue-resolution = { repository = "lettre/lettre" }
+is-it-maintained-open-issues = { repository = "lettre/lettre" }
+maintenance = { status = "actively-developed" }
+
+[dependencies]
+idna = "0.2"
+tracing = { version = "0.1.16", default-features = false, features = ["std"], optional = true } # feature
+
+# builder
+hyperx = { version = "1", optional = true, features = ["headers"] }
+mime = { version = "0.3.4", optional = true }
+uuid = { version = "0.8", features = ["v4"] }
+rand = { version = "0.8", optional = true }
+quoted_printable = { version = "0.4", optional = true }
+base64 = { version = "0.13", optional = true }
+once_cell = "1"
+regex = { version = "1", default-features = false, features = ["std", "unicode-case"] }
+
+# file transport
+serde = { version = "1", optional = true, features = ["derive"] }
+serde_json = { version = "1", optional = true }
+
+# smtp
+nom = { version = "6", default-features = false, features = ["alloc"], optional = true }
+r2d2 = { version = "0.8", optional = true } # feature
+hostname = { version = "0.3", optional = true } # feature
+
+## tls
+native-tls = { version = "0.2", optional = true } # feature
+rustls = { version = "0.19", features = ["dangerous_configuration"], optional = true }
+webpki = { version = "0.21", optional = true }
+webpki-roots = { version = "0.21", optional = true }
+
+# async
+futures-io = { version = "0.3.7", optional = true }
+futures-util = { version = "0.3.7", default-features = false, features = ["io"], optional = true }
+async-trait = { version = "0.1", optional = true }
+
+## async-std
+async-std = { version = "1.8", optional = true, features = ["unstable"] }
+#async-native-tls = { version = "0.3.3", optional = true }
+async-rustls = { version = "0.2", optional = true }
+
+## tokio
+tokio02_crate = { package = "tokio", version = "0.2.7", features = ["fs", "process", "tcp", "dns", "io-util"], optional = true }
+tokio02_native_tls_crate = { package = "tokio-native-tls", version = "0.1", optional = true }
+tokio02_rustls = { package = "tokio-rustls", version = "0.15", optional = true }
+tokio1_crate = { package = "tokio", version = "1", features = ["fs", "process", "net", "io-util"], optional = true }
+tokio1_native_tls_crate = { package = "tokio-native-tls", version = "0.3", optional = true }
+tokio1_rustls = { package = "tokio-rustls", version = "0.22", optional = true }
+
+[dev-dependencies]
+criterion = "0.3"
+tracing-subscriber = "0.2.10"
+glob = "0.3"
+walkdir = "2"
+tokio02_crate = { package = "tokio", version = "0.2.7", features = ["macros", "rt-threaded"] }
+tokio1_crate = { package = "tokio", version = "1", features = ["macros", "rt-multi-thread"] }
+async-std = { version = "1.8", features = ["attributes"] }
+serde_json = "1"
+maud = "0.22.1"
+
+[[bench]]
+harness = false
+name = "transport_smtp"
+
+[features]
+default = ["smtp-transport", "native-tls", "hostname", "r2d2", "builder"]
+builder = ["mime", "base64", "hyperx", "rand", "quoted_printable"]
+
+# transports
+file-transport = []
+file-transport-envelope = ["serde", "serde_json", "file-transport"]
+sendmail-transport = []
+smtp-transport = ["base64", "nom"]
+
+rustls-tls = ["webpki", "webpki-roots", "rustls"]
+
+# async
+async-std1 = ["async-std", "async-trait", "futures-io", "futures-util"]
+#async-std1-native-tls = ["async-std1", "native-tls", "async-native-tls"]
+async-std1-rustls-tls = ["async-std1", "rustls-tls", "async-rustls"]
+tokio02 = ["tokio02_crate", "async-trait", "futures-io", "futures-util"]
+tokio02-native-tls = ["tokio02", "native-tls", "tokio02_native_tls_crate"]
+tokio02-rustls-tls = ["tokio02", "rustls-tls", "tokio02_rustls"]
+tokio1 = ["tokio1_crate", "async-trait", "futures-io", "futures-util"]
+tokio1-native-tls = ["tokio1", "native-tls", "tokio1_native_tls_crate"]
+tokio1-rustls-tls = ["tokio1", "rustls-tls", "tokio1_rustls"]
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[[example]]
+name = "basic_html"
+required-features = ["file-transport", "builder"]
+
+[[example]]
+name = "maud_html"
+required-features = ["file-transport", "builder"]
+
+[[example]]
+name = "smtp"
+required-features = ["smtp-transport", "builder"]
+
+[[example]]
+name = "smtp_tls"
+required-features = ["smtp-transport", "native-tls", "builder"]
+
+[[example]]
+name = "smtp_starttls"
+required-features = ["smtp-transport", "native-tls", "builder"]
+
+[[example]]
+name = "smtp_selfsigned"
+required-features = ["smtp-transport", "native-tls", "builder"]
+
+[[example]]
+name = "tokio02_smtp_tls"
+required-features = ["smtp-transport", "tokio02", "tokio02-native-tls", "builder"]
+
+[[example]]
+name = "tokio02_smtp_starttls"
+required-features = ["smtp-transport", "tokio02", "tokio02-native-tls", "builder"]
+
+[[example]]
+name = "tokio1_smtp_tls"
+required-features = ["smtp-transport", "tokio1", "tokio1-native-tls", "builder"]
+
+[[example]]
+name = "tokio1_smtp_starttls"
+required-features = ["smtp-transport", "tokio1", "tokio1-native-tls", "builder"]
+
+[[example]]
+name = "asyncstd1_smtp_tls"
+required-features = ["smtp-transport", "async-std1", "async-std1-rustls-tls", "builder"]
+
+[[example]]
+name = "asyncstd1_smtp_starttls"
+required-features = ["smtp-transport", "async-std1", "async-std1-rustls-tls", "builder"]

LICENSE

@@ -1,4 +1,6 @@
-Copyright (c) 2014-2018 Alexis Mousset
+Copyright (c) 2014-2020 Alexis Mousset <contact@amousset.me>
+Copyright (c) 2019-2020 Paolo Barbolini <paolo@paolo565.org>
+Copyright (c) 2018 K. <kayo@illumium.org>
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated

README.md

@@ -1,25 +1,46 @@
-# lettre
+<h1 align="center">lettre</h1>
+<div align="center">
+ <strong>
+   A mailer library for Rust
+ </strong>
+</div>
 
-**Lettre is a mailer library for Rust.**
+<br />
 
-[![Build Status](https://travis-ci.org/lettre/lettre.svg?branch=master)](https://travis-ci.org/lettre/lettre)
-[![Build status](https://ci.appveyor.com/api/projects/status/mpwglemugjtkps2d/branch/master?svg=true)](https://ci.appveyor.com/project/amousset/lettre/branch/master)
-[![codecov](https://codecov.io/gh/lettre/lettre/branch/master/graph/badge.svg)](https://codecov.io/gh/lettre/lettre)
+<div align="center">
+  <a href="https://docs.rs/lettre">
+    <img src="https://docs.rs/lettre/badge.svg"
+      alt="docs" />
+  </a>
+  <a href="https://crates.io/crates/lettre">
+    <img src="https://img.shields.io/crates/d/lettre.svg"
+      alt="downloads" />
+  </a>
+  <br />
+  <a href="https://gitter.im/lettre/lettre">
+    <img src="https://badges.gitter.im/lettre/lettre.svg"
+      alt="chat on gitter" />
+  </a>
+  <a href="https://lettre.rs">
+    <img src="https://img.shields.io/badge/visit-website-blueviolet"
+      alt="website" />
+  </a>
+</div>
 
-[![Crate](https://img.shields.io/crates/v/lettre.svg)](https://crates.io/crates/lettre)
-[![Docs](https://docs.rs/lettre/badge.svg)](https://docs.rs/lettre/)
-[![Required Rust version](https://img.shields.io/badge/rustc-1.20-green.svg)]()
-[![MIT licensed](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE)
+<div align="center">
+  <a href="https://deps.rs/crate/lettre/0.10.0-beta.2">
+    <img src="https://deps.rs/crate/lettre/0.10.0-beta.2/status.svg"
+      alt="dependency status" />
+  </a>
+</div>
 
-[![Gitter](https://badges.gitter.im/lettre/lettre.svg)](https://gitter.im/lettre/lettre?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
-[![Average time to resolve an issue](http://isitmaintained.com/badge/resolution/lettre/lettre.svg)](http://isitmaintained.com/project/lettre/lettre "Average time to resolve an issue")
-[![Percentage of issues still open](http://isitmaintained.com/badge/open/lettre/lettre.svg)](http://isitmaintained.com/project/lettre/lettre "Percentage of issues still open")
+---
 
-Useful links:
-
-* [User documentation](http://lettre.at/)
-* [API documentation](https://docs.rs/lettre/)
-* [Changelog](https://github.com/lettre/lettre/blob/master/CHANGELOG.md)
+**NOTE**: this readme refers to the 0.10 version of lettre, which is
+still being worked on. The master branch and the alpha releases will see
+API breaking changes and some features may be missing or incomplete until
+the stable 0.10.0 release is out.
+Use the [`v0.9.x`](https://github.com/lettre/lettre/tree/v0.9.x) branch for stable releases.
 
 ---
 
@@ -31,50 +52,47 @@ Lettre provides the following features:
 * Unicode support (for email content and addresses)
 * Secure delivery with SMTP using encryption and authentication
 * Easy email builders
+* Async support
+
+Lettre does not provide (for now):
+
+* Email parsing
 
 ## Example
 
-This library requires Rust 1.26 or newer.
+This library requires Rust 1.45 or newer.
 To use this library, add the following to your `Cargo.toml`:
 
+
 ```toml
 [dependencies]
-lettre = "0.9"
-lettre_email = "0.9"
+lettre = "0.10.0-beta.2"
 ```
 
 ```rust,no_run
-extern crate lettre;
-extern crate lettre_email;
+use lettre::transport::smtp::authentication::Credentials;
+use lettre::{Message, SmtpTransport, Transport};
 
-use lettre::{EmailTransport, SmtpTransport};
-use lettre_email::EmailBuilder;
-use std::path::Path;
+let email = Message::builder()
+    .from("NoBody <nobody@domain.tld>".parse().unwrap())
+    .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+    .to("Hei <hei@domain.tld>".parse().unwrap())
+    .subject("Happy new year")
+    .body("Be happy!")
+    .unwrap();
 
-fn main() {
-    let email = EmailBuilder::new()
-        // Addresses can be specified by the tuple (email, alias)
-        .to(("user@example.org", "Firstname Lastname"))
-        // ... or by an address only
-        .from("user@example.com")
-        .subject("Hi, Hello world")
-        .text("Hello world.")
-        .build()
-        .unwrap();
+let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
-    // Open a local connection on port 25
-    let mut mailer = SmtpTransport::builder_unencrypted_localhost().unwrap()
-                                                                   .build();
-    // Send the email
-    let result = mailer.send(&email);
+// Open a remote connection to gmail
+let mailer = SmtpTransport::relay("smtp.gmail.com")
+    .unwrap()
+    .credentials(creds)
+    .build();
 
-    if result.is_ok() {
-        println!("Email sent");
-    } else {
-        println!("Could not send email: {:?}", result);
-    }
-
-    assert!(result.is_ok());
+// Send the email
+match mailer.send(&email) {
+    Ok(_) => println!("Email sent successfully!"),
+    Err(e) => panic!("Could not send email: {:?}", e),
 }
 ```
 
@@ -82,6 +100,8 @@ fn main() {
 
 The `lettre` tests require an open mail server listening locally on port 2525 and the `sendmail` command.
 
+Alternatively only unit tests can be run by doing `cargo test --lib`.
+
 ## Code of conduct
 
 Anyone who interacts with Lettre in any space, including but not limited to
@@ -91,4 +111,7 @@ this GitHub repository, must follow our [code of conduct](https://github.com/let
 
 This program is distributed under the terms of the MIT license.
 
+The builder comes from [emailmessage-rs](https://github.com/katyo/emailmessage-rs) by
+Kayo, under MIT license.
+
 See [LICENSE](./LICENSE) for details.

SECURITY.md

@@ -0,0 +1,9 @@
+## Report a security issue
+
+The lettre project team welcomes security reports and is committed to providing prompt attention to security issues.
+Security issues should be reported privately via [security@lettre.rs](mailto:security@lettre.rs). Security issues
+should not be reported via the public Github Issue tracker.
+
+## Security advisories
+
+Security issues will be announced via the [RustSec advisory database](https://github.com/RustSec/advisory-db).

benches/transport_smtp.rs

@@ -0,0 +1,44 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use lettre::{Message, SmtpTransport, Transport};
+
+fn bench_simple_send(c: &mut Criterion) {
+    let sender = SmtpTransport::builder_dangerous("127.0.0.1")
+        .port(2525)
+        .build();
+
+    c.bench_function("send email", move |b| {
+        b.iter(|| {
+            let email = Message::builder()
+                .from("NoBody <nobody@domain.tld>".parse().unwrap())
+                .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+                .to("Hei <hei@domain.tld>".parse().unwrap())
+                .subject("Happy new year")
+                .body(String::from("Be happy!"))
+                .unwrap();
+            let result = black_box(sender.send(&email));
+            assert!(result.is_ok());
+        })
+    });
+}
+
+fn bench_reuse_send(c: &mut Criterion) {
+    let sender = SmtpTransport::builder_dangerous("127.0.0.1")
+        .port(2525)
+        .build();
+    c.bench_function("send email with connection reuse", move |b| {
+        b.iter(|| {
+            let email = Message::builder()
+                .from("NoBody <nobody@domain.tld>".parse().unwrap())
+                .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+                .to("Hei <hei@domain.tld>".parse().unwrap())
+                .subject("Happy new year")
+                .body(String::from("Be happy!"))
+                .unwrap();
+            let result = black_box(sender.send(&email));
+            assert!(result.is_ok());
+        })
+    });
+}
+
+criterion_group!(benches, bench_simple_send, bench_reuse_send);
+criterion_main!(benches);

examples/README.md

@@ -0,0 +1,24 @@
+# Lettre Examples
+
+This folder contains examples showing how to use lettre in your own projects.
+
+## Message builder examples
+
+- [basic_html.rs] - Create an HTML email.
+- [maud_html.rs] - Create an HTML email using a [maud](https://github.com/lambda-fairy/maud) template.
+
+## SMTP Examples
+
+- [smtp.rs] - Send an email using a local SMTP daemon on port 25 as a relay.
+- [smtp_tls.rs] - Send an email over SMTP encrypted with TLS and authenticating with username and password.
+- [smtp_starttls.rs] - Send an email over SMTP with STARTTLS and authenticating with username and password.
+- [smtp_selfsigned.rs] - Send an email over SMTP encrypted with TLS using a self-signed certificate and authenticating with username and password.
+- The [smtp_tls.rs] and [smtp_starttls.rs] examples also feature `async`hronous implementations powered by [Tokio](https://tokio.rs/).
+  These files are prefixed with `tokio02_`, `tokio1_` or `asyncstd1_`.
+
+[basic_html.rs]: ./basic_html.rs
+[maud_html.rs]: ./maud_html.rs
+[smtp.rs]: ./smtp.rs
+[smtp_tls.rs]: ./smtp_tls.rs
+[smtp_starttls.rs]: ./smtp_starttls.rs
+[smtp_selfsigned.rs]: ./smtp_selfsigned.rs

examples/asyncstd1_smtp_starttls.rs

@@ -0,0 +1,32 @@
+use lettre::{
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncStd1Executor,
+    AsyncTransport, Message,
+};
+
+#[async_std::main]
+async fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new async year")
+        .body(String::from("Be happy with async!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail using STARTTLS
+    let mailer: AsyncSmtpTransport<AsyncStd1Executor> =
+        AsyncSmtpTransport::<AsyncStd1Executor>::starttls_relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
+
+    // Send the email
+    match mailer.send(email).await {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/asyncstd1_smtp_tls.rs

@@ -0,0 +1,32 @@
+use lettre::{
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncStd1Executor,
+    AsyncTransport, Message,
+};
+
+#[async_std::main]
+async fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new async year")
+        .body(String::from("Be happy with async!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail
+    let mailer: AsyncSmtpTransport<AsyncStd1Executor> =
+        AsyncSmtpTransport::<AsyncStd1Executor>::relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
+
+    // Send the email
+    match mailer.send(email).await {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/basic_html.rs

@@ -0,0 +1,53 @@
+use lettre::{
+    message::{header, MultiPart, SinglePart},
+    FileTransport, Message, Transport,
+};
+
+fn main() {
+    // The html we want to send.
+    let html = r#"<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Hello from Lettre!</title>
+</head>
+<body>
+    <div style="display: flex; flex-direction: column; align-items: center;">
+        <h2 style="font-family: Arial, Helvetica, sans-serif;">Hello from Lettre!</h2>
+        <h4 style="font-family: Arial, Helvetica, sans-serif;">A mailer library for Rust</h4>
+    </div>
+</body>
+</html>"#;
+
+    // Build the message.
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Hello from Lettre!")
+        .multipart(
+            MultiPart::alternative() // This is composed of two parts.
+                .singlepart(
+                    SinglePart::builder()
+                        .header(header::ContentType(
+                            "text/plain; charset=utf8".parse().unwrap(),
+                        ))
+                        .body(String::from("Hello from Lettre! A mailer library for Rust")), // Every message should have a plain text fallback.
+                )
+                .singlepart(
+                    SinglePart::builder()
+                        .header(header::ContentType(
+                            "text/html; charset=utf8".parse().unwrap(),
+                        ))
+                        .body(String::from(html)),
+                ),
+        )
+        .expect("failed to build email");
+
+    // Create our mailer. Please see the other examples for creating SMTP mailers.
+    // The path given here must exist on the filesystem.
+    let mailer = FileTransport::new("./");
+
+    // Store the message when you're ready.
+    mailer.send(&email).expect("failed to deliver message");
+}

examples/maud_html.rs

@@ -0,0 +1,62 @@
+use lettre::{
+    message::{header, MultiPart, SinglePart},
+    FileTransport, Message, Transport,
+};
+use maud::html;
+
+fn main() {
+    // The recipient's name. We might obtain this from a form or their email address.
+    let recipient = "Hei";
+
+    // Create the html we want to send.
+    let html = html! {
+        head {
+            title { "Hello from Lettre!" }
+            style type="text/css" {
+                "h2, h4 { font-family: Arial, Helvetica, sans-serif; }"
+            }
+        }
+        div style="display: flex; flex-direction: column; align-items: center;" {
+            h2 { "Hello from Lettre!" }
+            // Substitute in the name of our recipient.
+            p { "Dear " (recipient) "," }
+            p { "This email was sent with Lettre, a mailer library for Rust!"}
+            p {
+                "This example uses "
+                a href="https://crates.io/crates/maud" { "maud" }
+                ". It is about 20% cooler than the basic HTML example."
+            }
+        }
+    };
+
+    // Build the message.
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Hello from Lettre!")
+        .multipart(
+            MultiPart::alternative() // This is composed of two parts.
+                .singlepart(
+                    SinglePart::builder()
+                        .header(header::ContentType(
+                            "text/plain; charset=utf8".parse().unwrap(),
+                        ))
+                        .body(String::from("Hello from Lettre! A mailer library for Rust")), // Every message should have a plain text fallback.
+                )
+                .singlepart(
+                    SinglePart::builder()
+                        .header(header::ContentType(
+                            "text/html; charset=utf8".parse().unwrap(),
+                        ))
+                        .body(html.into_string()),
+                ),
+        )
+        .expect("failed to build email");
+
+    // Create our mailer. Please see the other examples for creating SMTP mailers.
+    // The path given here must exist on the filesystem.
+    let mailer = FileTransport::new("./");
+
+    // Store the message when you're ready.
+    mailer.send(&email).expect("failed to deliver message");
+}

examples/smtp.rs

@@ -0,0 +1,22 @@
+use lettre::{Message, SmtpTransport, Transport};
+
+fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new year")
+        .body(String::from("Be happy!"))
+        .unwrap();
+
+    // Open a local connection on port 25
+    let mailer = SmtpTransport::unencrypted_localhost();
+
+    // Send the email
+    match mailer.send(&email) {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/smtp_selfsigned.rs

@@ -0,0 +1,44 @@
+use std::fs;
+
+use lettre::{
+    transport::smtp::{
+        authentication::Credentials,
+        client::{Certificate, Tls, TlsParameters},
+    },
+    Message, SmtpTransport, Transport,
+};
+
+fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new year")
+        .body(String::from("Be happy!"))
+        .unwrap();
+
+    // Use a custom certificate stored on disk to securely verify the server's certificate
+    let pem_cert = fs::read("certificate.pem").unwrap();
+    let cert = Certificate::from_pem(&pem_cert).unwrap();
+    let tls = TlsParameters::builder("smtp.server.com".to_string())
+        .add_root_certificate(cert)
+        .build()
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to the smtp server
+    let mailer = SmtpTransport::builder_dangerous("smtp.server.com")
+        .port(465)
+        .tls(Tls::Wrapper(tls))
+        .credentials(creds)
+        .build();
+
+    // Send the email
+    match mailer.send(&email) {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/smtp_starttls.rs

@@ -0,0 +1,27 @@
+use lettre::{transport::smtp::authentication::Credentials, Message, SmtpTransport, Transport};
+
+fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new year")
+        .body(String::from("Be happy!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail using STARTTLS
+    let mailer = SmtpTransport::starttls_relay("smtp.gmail.com")
+        .unwrap()
+        .credentials(creds)
+        .build();
+
+    // Send the email
+    match mailer.send(&email) {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/smtp_tls.rs

@@ -0,0 +1,27 @@
+use lettre::{transport::smtp::authentication::Credentials, Message, SmtpTransport, Transport};
+
+fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new year")
+        .body(String::from("Be happy!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail
+    let mailer = SmtpTransport::relay("smtp.gmail.com")
+        .unwrap()
+        .credentials(creds)
+        .build();
+
+    // Send the email
+    match mailer.send(&email) {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/tokio02_smtp_starttls.rs

@@ -0,0 +1,37 @@
+// This line is only to make it compile from lettre's examples folder,
+// since it uses Rust 2018 crate renaming to import tokio.
+// Won't be needed in user's code.
+use tokio02_crate as tokio;
+
+use lettre::{
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncTransport, Message,
+    Tokio02Executor,
+};
+
+#[tokio::main]
+async fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new async year")
+        .body(String::from("Be happy with async!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail using STARTTLS
+    let mailer: AsyncSmtpTransport<Tokio02Executor> =
+        AsyncSmtpTransport::<Tokio02Executor>::starttls_relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
+
+    // Send the email
+    match mailer.send(email).await {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/tokio02_smtp_tls.rs

@@ -0,0 +1,37 @@
+// This line is only to make it compile from lettre's examples folder,
+// since it uses Rust 2018 crate renaming to import tokio.
+// Won't be needed in user's code.
+use tokio02_crate as tokio;
+
+use lettre::{
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncTransport, Message,
+    Tokio02Executor,
+};
+
+#[tokio::main]
+async fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new async year")
+        .body(String::from("Be happy with async!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail
+    let mailer: AsyncSmtpTransport<Tokio02Executor> =
+        AsyncSmtpTransport::<Tokio02Executor>::relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
+
+    // Send the email
+    match mailer.send(email).await {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/tokio1_smtp_starttls.rs

@@ -0,0 +1,37 @@
+// This line is only to make it compile from lettre's examples folder,
+// since it uses Rust 2018 crate renaming to import tokio.
+// Won't be needed in user's code.
+use tokio1_crate as tokio;
+
+use lettre::{
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncTransport, Message,
+    Tokio1Executor,
+};
+
+#[tokio::main]
+async fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new async year")
+        .body(String::from("Be happy with async!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail using STARTTLS
+    let mailer: AsyncSmtpTransport<Tokio1Executor> =
+        AsyncSmtpTransport::<Tokio1Executor>::starttls_relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
+
+    // Send the email
+    match mailer.send(email).await {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

examples/tokio1_smtp_tls.rs

@@ -0,0 +1,37 @@
+// This line is only to make it compile from lettre's examples folder,
+// since it uses Rust 2018 crate renaming to import tokio.
+// Won't be needed in user's code.
+use tokio1_crate as tokio;
+
+use lettre::{
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncTransport, Message,
+    Tokio1Executor,
+};
+
+#[tokio::main]
+async fn main() {
+    tracing_subscriber::fmt::init();
+
+    let email = Message::builder()
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .to("Hei <hei@domain.tld>".parse().unwrap())
+        .subject("Happy new async year")
+        .body(String::from("Be happy with async!"))
+        .unwrap();
+
+    let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
+
+    // Open a remote connection to gmail
+    let mailer: AsyncSmtpTransport<Tokio1Executor> =
+        AsyncSmtpTransport::<Tokio1Executor>::relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
+
+    // Send the email
+    match mailer.send(email).await {
+        Ok(_) => println!("Email sent successfully!"),
+        Err(e) => panic!("Could not send email: {:?}", e),
+    }
+}

lettre/CHANGELOG.md

@@ -1 +0,0 @@
-../CHANGELOG.md

lettre/Cargo.toml

@@ -1,55 +0,0 @@
-[package]
-
-name = "lettre"
-version = "0.9.0" # remember to update html_root_url
-description = "Email client"
-readme = "README.md"
-homepage = "http://lettre.at"
-repository = "https://github.com/lettre/lettre"
-license = "MIT"
-authors = ["Alexis Mousset <contact@amousset.me>"]
-categories = ["email"]
-keywords = ["email", "smtp", "mailer"]
-
-[badges]
-travis-ci = { repository = "lettre/lettre" }
-appveyor = { repository = "lettre/lettre" }
-maintenance = { status = "actively-developed" }
-is-it-maintained-issue-resolution = { repository = "lettre/lettre" }
-is-it-maintained-open-issues = { repository = "lettre/lettre" }
-
-[dependencies]
-log = "^0.4"
-nom = { version = "^4.0", optional = true }
-bufstream = { version = "^0.1", optional = true }
-native-tls = { version = "^0.2", optional = true }
-base64 = { version = "^0.10", optional = true }
-hostname = { version = "^0.1", optional = true }
-serde = { version = "^1.0", optional = true }
-serde_json = { version = "^1.0", optional = true }
-serde_derive = { version = "^1.0", optional = true }
-failure = "^0.1"
-failure_derive = "^0.1"
-fast_chemail = "^0.9"
-r2d2 = { version = "^0.8", optional = true}
-
-[dev-dependencies]
-env_logger = "^0.6"
-glob = "0.3"
-
-[features]
-default = ["file-transport", "smtp-transport", "sendmail-transport"]
-unstable = []
-serde-impls = ["serde", "serde_derive"]
-file-transport = ["serde-impls", "serde_json"]
-smtp-transport = ["bufstream", "native-tls", "base64", "nom", "hostname"]
-sendmail-transport = []
-connection-pool = [ "r2d2" ]
-
-[[example]]
-name = "smtp"
-required-features = ["smtp-transport"]
-
-[[example]]
-name = "smtp_gmail"
-required-features = ["smtp-transport"]

lettre/LICENSE

@@ -1 +0,0 @@
-../LICENSE

lettre/README.md

@@ -1 +0,0 @@
-../README.md

lettre/benches/transport_smtp.rs

@@ -1,50 +0,0 @@
-#![feature(test)]
-
-extern crate lettre;
-extern crate test;
-
-use lettre::smtp::ConnectionReuseParameters;
-use lettre::{ClientSecurity, Envelope, SmtpTransport};
-use lettre::{EmailAddress, SendableEmail, Transport};
-
-#[bench]
-fn bench_simple_send(b: &mut test::Bencher) {
-    let mut sender = SmtpTransport::builder("127.0.0.1:2525", ClientSecurity::None)
-        .unwrap()
-        .build();
-    b.iter(|| {
-        let email = SendableEmail::new(
-            Envelope::new(
-                Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-                vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-            )
-            .unwrap(),
-            "id".to_string(),
-            "Hello ß☺ example".to_string().into_bytes(),
-        );
-        let result = sender.send(email);
-        assert!(result.is_ok());
-    });
-}
-
-#[bench]
-fn bench_reuse_send(b: &mut test::Bencher) {
-    let mut sender = SmtpTransport::builder("127.0.0.1:2525", ClientSecurity::None)
-        .unwrap()
-        .connection_reuse(ConnectionReuseParameters::ReuseUnlimited)
-        .build();
-    b.iter(|| {
-        let email = SendableEmail::new(
-            Envelope::new(
-                Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-                vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-            )
-            .unwrap(),
-            "id".to_string(),
-            "Hello ß☺ example".to_string().into_bytes(),
-        );
-        let result = sender.send(email);
-        assert!(result.is_ok());
-    });
-    sender.close()
-}

lettre/examples/smtp.rs

@@ -1,31 +0,0 @@
-extern crate env_logger;
-extern crate lettre;
-
-use lettre::{EmailAddress, Envelope, SendableEmail, SmtpClient, Transport};
-
-fn main() {
-    env_logger::init();
-
-    let email = SendableEmail::new(
-        Envelope::new(
-            Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-            vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-        )
-        .unwrap(),
-        "id".to_string(),
-        "Hello ß☺ example".to_string().into_bytes(),
-    );
-
-    // Open a local connection on port 25
-    let mut mailer = SmtpClient::new_unencrypted_localhost().unwrap().transport();
-    // Send the email
-    let result = mailer.send(email);
-
-    if result.is_ok() {
-        println!("Email sent");
-    } else {
-        println!("Could not send email: {:?}", result);
-    }
-
-    assert!(result.is_ok());
-}

lettre/examples/smtp_gmail.rs

@@ -1,38 +0,0 @@
-extern crate lettre;
-
-use lettre::smtp::authentication::Credentials;
-use lettre::{EmailAddress, Envelope, SendableEmail, SmtpClient, Transport};
-
-fn main() {
-    let email = SendableEmail::new(
-        Envelope::new(
-            Some(EmailAddress::new("from@gmail.com".to_string()).unwrap()),
-            vec![EmailAddress::new("to@example.com".to_string()).unwrap()],
-        )
-        .unwrap(),
-        "id".to_string(),
-        "Hello example".to_string().into_bytes(),
-    );
-
-    let creds = Credentials::new(
-        "example_username".to_string(),
-        "example_password".to_string(),
-    );
-
-    // Open a remote connection to gmail
-    let mut mailer = SmtpClient::new_simple("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .transport();
-
-    // Send the email
-    let result = mailer.send(email);
-
-    if result.is_ok() {
-        println!("Email sent");
-    } else {
-        println!("Could not send email: {:?}", result);
-    }
-
-    assert!(result.is_ok());
-}

lettre/src/error.rs

@@ -1,18 +0,0 @@
-use failure;
-
-/// Error type for email content
-#[derive(Fail, Debug, Clone, Copy)]
-pub enum Error {
-    /// Missing from in envelope
-    #[fail(display = "missing source address, invalid envelope")]
-    MissingFrom,
-    /// Missing to in envelope
-    #[fail(display = "missing destination address, invalid envelope")]
-    MissingTo,
-    /// Invalid email
-    #[fail(display = "invalid email address")]
-    InvalidEmailAddress,
-}
-
-/// Email result type
-pub type EmailResult<T> = Result<T, failure::Error>;

lettre/src/file/error.rs

@@ -1,40 +0,0 @@
-//! Error and result type for file transport
-
-use failure;
-use serde_json;
-use std::io;
-
-/// An enum of all error kinds.
-#[derive(Fail, Debug)]
-pub enum Error {
-    /// Internal client error
-    #[fail(display = "Internal client error: {}", error)]
-    Client { error: &'static str },
-    /// IO error
-    #[fail(display = "IO error: {}", error)]
-    Io { error: io::Error },
-    /// JSON serialization error
-    #[fail(display = "JSON serialization error: {}", error)]
-    JsonSerialization { error: serde_json::Error },
-}
-
-impl From<io::Error> for Error {
-    fn from(err: io::Error) -> Error {
-        Error::Io { error: err }
-    }
-}
-
-impl From<serde_json::Error> for Error {
-    fn from(err: serde_json::Error) -> Error {
-        Error::JsonSerialization { error: err }
-    }
-}
-
-impl From<&'static str> for Error {
-    fn from(string: &'static str) -> Error {
-        Error::Client { error: string }
-    }
-}
-
-/// SMTP result type
-pub type FileResult = Result<(), failure::Error>;

lettre/src/file/mod.rs

@@ -1,60 +0,0 @@
-//! The file transport writes the emails to the given directory. The name of the file will be
-//! `message_id.txt`.
-//! It can be useful for testing purposes, or if you want to keep track of sent messages.
-//!
-
-use file::error::FileResult;
-use serde_json;
-use std::fs::File;
-use std::io::prelude::*;
-use std::path::{Path, PathBuf};
-use Envelope;
-use SendableEmail;
-use Transport;
-
-pub mod error;
-
-/// Writes the content and the envelope information to a file
-#[derive(Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct FileTransport {
-    path: PathBuf,
-}
-
-impl FileTransport {
-    /// Creates a new transport to the given directory
-    pub fn new<P: AsRef<Path>>(path: P) -> FileTransport {
-        FileTransport {
-            path: PathBuf::from(path.as_ref()),
-        }
-    }
-}
-
-#[derive(PartialEq, Eq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-struct SerializableEmail {
-    envelope: Envelope,
-    message_id: String,
-    message: Vec<u8>,
-}
-
-impl<'a> Transport<'a> for FileTransport {
-    type Result = FileResult;
-
-    fn send(&mut self, email: SendableEmail) -> FileResult {
-        let message_id = email.message_id().to_string();
-        let envelope = email.envelope().clone();
-
-        let mut file = self.path.clone();
-        file.push(format!("{}.json", message_id));
-
-        let serialized = serde_json::to_string(&SerializableEmail {
-            envelope,
-            message_id,
-            message: email.message_to_string()?.as_bytes().to_vec(),
-        })?;
-
-        File::create(file.as_path())?.write_all(serialized.as_bytes())?;
-        Ok(())
-    }
-}

lettre/src/lib.rs

@@ -1,217 +0,0 @@
-//! Lettre is a mailer written in Rust. It provides a simple email builder and several transports.
-//!
-//! This mailer contains the available transports for your emails.
-//!
-
-#![doc(html_root_url = "https://docs.rs/lettre/0.9.0")]
-#![deny(
-    missing_copy_implementations,
-    trivial_casts,
-    trivial_numeric_casts,
-    unsafe_code,
-    unstable_features,
-    unused_import_braces
-)]
-#[cfg(feature = "smtp-transport")]
-extern crate base64;
-#[cfg(feature = "smtp-transport")]
-extern crate bufstream;
-#[cfg(feature = "smtp-transport")]
-extern crate hostname;
-#[macro_use]
-extern crate log;
-#[cfg(feature = "smtp-transport")]
-extern crate native_tls;
-#[cfg(feature = "smtp-transport")]
-#[macro_use]
-extern crate nom;
-#[cfg(feature = "serde-impls")]
-extern crate serde;
-#[cfg(feature = "serde-impls")]
-#[macro_use]
-extern crate serde_derive;
-extern crate failure;
-#[cfg(feature = "file-transport")]
-extern crate serde_json;
-#[macro_use]
-extern crate failure_derive;
-extern crate fast_chemail;
-#[cfg(feature = "connection-pool")]
-extern crate r2d2;
-
-pub mod error;
-#[cfg(feature = "file-transport")]
-pub mod file;
-#[cfg(feature = "sendmail-transport")]
-pub mod sendmail;
-#[cfg(feature = "smtp-transport")]
-pub mod smtp;
-pub mod stub;
-
-use error::EmailResult;
-use error::Error as EmailError;
-use failure::Error;
-use fast_chemail::is_valid_email;
-#[cfg(feature = "file-transport")]
-pub use file::FileTransport;
-#[cfg(feature = "sendmail-transport")]
-pub use sendmail::SendmailTransport;
-#[cfg(feature = "smtp-transport")]
-pub use smtp::client::net::ClientTlsParameters;
-#[cfg(all(feature = "smtp-transport", feature = "connection-pool"))]
-pub use smtp::r2d2::SmtpConnectionManager;
-#[cfg(feature = "smtp-transport")]
-pub use smtp::{ClientSecurity, SmtpClient, SmtpTransport};
-use std::ffi::OsStr;
-use std::fmt::{self, Display, Formatter};
-use std::io;
-use std::io::Cursor;
-use std::io::Read;
-use std::str::FromStr;
-
-/// Email address
-#[derive(PartialEq, Eq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct EmailAddress(String);
-
-impl EmailAddress {
-    pub fn new(address: String) -> EmailResult<EmailAddress> {
-        if !is_valid_email(&address) && !address.ends_with("localhost") {
-            Err(EmailError::InvalidEmailAddress)?;
-        }
-        Ok(EmailAddress(address))
-    }
-}
-
-impl FromStr for EmailAddress {
-    type Err = Error;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        EmailAddress::new(s.to_string())
-    }
-}
-
-impl Display for EmailAddress {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.write_str(&self.0)
-    }
-}
-
-impl AsRef<str> for EmailAddress {
-    fn as_ref(&self) -> &str {
-        &self.0
-    }
-}
-
-impl AsRef<OsStr> for EmailAddress {
-    fn as_ref(&self) -> &OsStr {
-        &self.0.as_ref()
-    }
-}
-
-/// Simple email envelope representation
-///
-/// We only accept mailboxes, and do not support source routes (as per RFC).
-#[derive(PartialEq, Eq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct Envelope {
-    /// The envelope recipients' addresses
-    ///
-    /// This can not be empty.
-    forward_path: Vec<EmailAddress>,
-    /// The envelope sender address
-    reverse_path: Option<EmailAddress>,
-}
-
-impl Envelope {
-    /// Creates a new envelope, which may fail if `to` is empty.
-    pub fn new(from: Option<EmailAddress>, to: Vec<EmailAddress>) -> EmailResult<Envelope> {
-        if to.is_empty() {
-            Err(EmailError::MissingTo)?;
-        }
-        Ok(Envelope {
-            forward_path: to,
-            reverse_path: from,
-        })
-    }
-
-    /// Destination addresses of the envelope
-    pub fn to(&self) -> &[EmailAddress] {
-        self.forward_path.as_slice()
-    }
-
-    /// Source address of the envelope
-    pub fn from(&self) -> Option<&EmailAddress> {
-        self.reverse_path.as_ref()
-    }
-}
-
-pub enum Message {
-    Reader(Box<Read + Send>),
-    Bytes(Cursor<Vec<u8>>),
-}
-
-impl Read for Message {
-    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        match *self {
-            Message::Reader(ref mut rdr) => rdr.read(buf),
-            Message::Bytes(ref mut rdr) => rdr.read(buf),
-        }
-    }
-}
-
-/// Sendable email structure
-pub struct SendableEmail {
-    envelope: Envelope,
-    message_id: String,
-    message: Message,
-}
-
-impl SendableEmail {
-    pub fn new(envelope: Envelope, message_id: String, message: Vec<u8>) -> SendableEmail {
-        SendableEmail {
-            envelope,
-            message_id,
-            message: Message::Bytes(Cursor::new(message)),
-        }
-    }
-
-    pub fn new_with_reader(
-        envelope: Envelope,
-        message_id: String,
-        message: Box<Read + Send>,
-    ) -> SendableEmail {
-        SendableEmail {
-            envelope,
-            message_id,
-            message: Message::Reader(message),
-        }
-    }
-
-    pub fn envelope(&self) -> &Envelope {
-        &self.envelope
-    }
-
-    pub fn message_id(&self) -> &str {
-        &self.message_id
-    }
-
-    pub fn message(self) -> Message {
-        self.message
-    }
-
-    pub fn message_to_string(mut self) -> Result<String, io::Error> {
-        let mut message_content = String::new();
-        self.message.read_to_string(&mut message_content)?;
-        Ok(message_content)
-    }
-}
-
-/// Transport method for emails
-pub trait Transport<'a> {
-    /// Result type for the transport
-    type Result;
-
-    /// Sends the email
-    fn send(&mut self, email: SendableEmail) -> Self::Result;
-}

lettre/src/sendmail/error.rs

@@ -1,30 +0,0 @@
-//! Error and result type for sendmail transport
-
-use failure;
-use std::io;
-
-/// An enum of all error kinds.
-#[derive(Fail, Debug)]
-pub enum Error {
-    /// Internal client error
-    #[fail(display = "Internal client error: {}", error)]
-    Client { error: &'static str },
-    /// IO error
-    #[fail(display = "IO error: {}", error)]
-    Io { error: io::Error },
-}
-
-impl From<io::Error> for Error {
-    fn from(err: io::Error) -> Error {
-        Error::Io { error: err }
-    }
-}
-
-impl From<&'static str> for Error {
-    fn from(string: &'static str) -> Error {
-        Error::Client { error: string }
-    }
-}
-
-/// sendmail result type
-pub type SendmailResult = Result<(), failure::Error>;

lettre/src/sendmail/mod.rs

@@ -1,80 +0,0 @@
-//! The sendmail transport sends the email using the local sendmail command.
-//!
-
-use sendmail::error::SendmailResult;
-use std::io::prelude::*;
-use std::io::Read;
-use std::process::{Command, Stdio};
-use SendableEmail;
-use Transport;
-
-pub mod error;
-
-/// Sends an email using the `sendmail` command
-#[derive(Debug, Default)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct SendmailTransport {
-    command: String,
-}
-
-impl SendmailTransport {
-    /// Creates a new transport with the default `/usr/sbin/sendmail` command
-    pub fn new() -> SendmailTransport {
-        SendmailTransport {
-            command: "/usr/sbin/sendmail".to_string(),
-        }
-    }
-
-    /// Creates a new transport to the given sendmail command
-    pub fn new_with_command<S: Into<String>>(command: S) -> SendmailTransport {
-        SendmailTransport {
-            command: command.into(),
-        }
-    }
-}
-
-impl<'a> Transport<'a> for SendmailTransport {
-    type Result = SendmailResult;
-
-    fn send(&mut self, email: SendableEmail) -> SendmailResult {
-        let message_id = email.message_id().to_string();
-
-        // Spawn the sendmail command
-        let mut process = Command::new(&self.command)
-            .arg("-i")
-            .arg("-f")
-            .arg(
-                email
-                    .envelope()
-                    .from()
-                    .map(|x| x.as_ref())
-                    .unwrap_or("\"\""),
-            )
-            .args(email.envelope.to())
-            .stdin(Stdio::piped())
-            .stdout(Stdio::piped())
-            .spawn()?;
-
-        let mut message_content = String::new();
-        let _ = email.message().read_to_string(&mut message_content);
-
-        process
-            .stdin
-            .as_mut()
-            .unwrap()
-            .write_all(message_content.as_bytes())?;
-
-        info!("Wrote {} message to stdin", message_id);
-
-        let output = process.wait_with_output()?;
-
-        if output.status.success() {
-            Ok(())
-        } else {
-            // TODO display stderr
-            Err(error::Error::Client {
-                error: "The message could not be sent",
-            })?
-        }
-    }
-}

lettre/src/smtp/client/mod.rs

@@ -1,312 +0,0 @@
-//! SMTP client
-
-use bufstream::BufStream;
-use nom::ErrorKind as NomErrorKind;
-use smtp::authentication::{Credentials, Mechanism};
-use smtp::client::net::{ClientTlsParameters, Connector, NetworkStream, Timeout};
-use smtp::commands::*;
-use smtp::error::{Error, SmtpResult};
-use smtp::response::Response;
-use std::fmt::{Debug, Display};
-use std::io::{self, BufRead, BufReader, Read, Write};
-use std::net::ToSocketAddrs;
-use std::string::String;
-use std::time::Duration;
-
-pub mod mock;
-pub mod net;
-
-/// The codec used for transparency
-#[derive(Default, Clone, Copy, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct ClientCodec {
-    escape_count: u8,
-}
-
-impl ClientCodec {
-    /// Creates a new client codec
-    pub fn new() -> Self {
-        ClientCodec::default()
-    }
-}
-
-impl ClientCodec {
-    /// Adds transparency
-    /// TODO: replace CR and LF by CRLF
-    fn encode(&mut self, frame: &[u8], buf: &mut Vec<u8>) -> Result<(), Error> {
-        match frame.len() {
-            0 => {
-                match self.escape_count {
-                    0 => buf.write_all(b"\r\n.\r\n")?,
-                    1 => buf.write_all(b"\n.\r\n")?,
-                    2 => buf.write_all(b".\r\n")?,
-                    _ => unreachable!(),
-                }
-                self.escape_count = 0;
-                Ok(())
-            }
-            _ => {
-                let mut start = 0;
-                for (idx, byte) in frame.iter().enumerate() {
-                    match self.escape_count {
-                        0 => self.escape_count = if *byte == b'\r' { 1 } else { 0 },
-                        1 => self.escape_count = if *byte == b'\n' { 2 } else { 0 },
-                        2 => self.escape_count = if *byte == b'.' { 3 } else { 0 },
-                        _ => unreachable!(),
-                    }
-                    if self.escape_count == 3 {
-                        self.escape_count = 0;
-                        buf.write_all(&frame[start..idx])?;
-                        buf.write_all(b".")?;
-                        start = idx;
-                    }
-                }
-                buf.write_all(&frame[start..])?;
-                Ok(())
-            }
-        }
-    }
-}
-
-/// Returns the string replacing all the CRLF with "\<CRLF\>"
-/// Used for debug displays
-fn escape_crlf(string: &str) -> String {
-    string.replace("\r\n", "<CRLF>")
-}
-
-/// Structure that implements the SMTP client
-#[derive(Debug, Default)]
-pub struct InnerClient<S: Write + Read = NetworkStream> {
-    /// TCP stream between client and server
-    /// Value is None before connection
-    stream: Option<BufStream<S>>,
-}
-
-macro_rules! return_err (
-    ($err: expr, $client: ident) => ({
-        return Err(From::from($err))
-    })
-);
-
-#[cfg_attr(feature = "cargo-clippy", allow(clippy::new_without_default_derive))]
-impl<S: Write + Read> InnerClient<S> {
-    /// Creates a new SMTP client
-    ///
-    /// It does not connects to the server, but only creates the `Client`
-    pub fn new() -> InnerClient<S> {
-        InnerClient { stream: None }
-    }
-}
-
-impl<S: Connector + Write + Read + Timeout + Debug> InnerClient<S> {
-    /// Closes the SMTP transaction if possible
-    pub fn close(&mut self) {
-        let _ = self.command(QuitCommand);
-        self.stream = None;
-    }
-
-    /// Sets the underlying stream
-    pub fn set_stream(&mut self, stream: S) {
-        self.stream = Some(BufStream::new(stream));
-    }
-
-    /// Upgrades the underlying connection to SSL/TLS
-    pub fn upgrade_tls_stream(&mut self, tls_parameters: &ClientTlsParameters) -> io::Result<()> {
-        match self.stream {
-            Some(ref mut stream) => stream.get_mut().upgrade_tls(tls_parameters),
-            None => Ok(()),
-        }
-    }
-
-    /// Tells if the underlying stream is currently encrypted
-    pub fn is_encrypted(&self) -> bool {
-        match self.stream {
-            Some(ref stream) => stream.get_ref().is_encrypted(),
-            None => false,
-        }
-    }
-
-    /// Set timeout
-    pub fn set_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
-        match self.stream {
-            Some(ref mut stream) => {
-                stream.get_mut().set_read_timeout(duration)?;
-                stream.get_mut().set_write_timeout(duration)?;
-                Ok(())
-            }
-            None => Ok(()),
-        }
-    }
-
-    /// Connects to the configured server
-    pub fn connect<A: ToSocketAddrs>(
-        &mut self,
-        addr: &A,
-        tls_parameters: Option<&ClientTlsParameters>,
-    ) -> SmtpResult {
-        // Connect should not be called when the client is already connected
-        if self.stream.is_some() {
-            return_err!("The connection is already established", self);
-        }
-
-        let mut addresses = addr.to_socket_addrs()?;
-
-        let server_addr = match addresses.next() {
-            Some(addr) => addr,
-            None => return_err!("Could not resolve hostname", self),
-        };
-
-        debug!("connecting to {}", server_addr);
-
-        // Try to connect
-        self.set_stream(Connector::connect(&server_addr, tls_parameters)?);
-
-        self.read_response()
-    }
-
-    /// Checks if the server is connected using the NOOP SMTP command
-    #[cfg_attr(feature = "cargo-clippy", allow(clippy::wrong_self_convention))]
-    pub fn is_connected(&mut self) -> bool {
-        self.stream.is_some() && self.command(NoopCommand).is_ok()
-    }
-
-    /// Sends an AUTH command with the given mechanism, and handles challenge if needed
-    pub fn auth(&mut self, mechanism: Mechanism, credentials: &Credentials) -> SmtpResult {
-        // TODO
-        let mut challenges = 10;
-        let mut response = self.command(AuthCommand::new(mechanism, credentials.clone(), None)?)?;
-
-        while challenges > 0 && response.has_code(334) {
-            challenges -= 1;
-            response = self.command(AuthCommand::new_from_response(
-                mechanism,
-                credentials.clone(),
-                &response,
-            )?)?;
-        }
-
-        if challenges == 0 {
-            Err(Error::ResponseParsing("Unexpected number of challenges"))
-        } else {
-            Ok(response)
-        }
-    }
-
-    /// Sends the message content
-    pub fn message(&mut self, message: Box<Read>) -> SmtpResult {
-        let mut out_buf: Vec<u8> = vec![];
-        let mut codec = ClientCodec::new();
-
-        let mut message_reader = BufReader::new(message);
-
-        loop {
-            out_buf.clear();
-
-            let consumed = match message_reader.fill_buf() {
-                Ok(bytes) => {
-                    codec.encode(bytes, &mut out_buf)?;
-                    bytes.len()
-                }
-                Err(ref err) => panic!("Failed with: {}", err),
-            };
-            message_reader.consume(consumed);
-
-            if consumed == 0 {
-                break;
-            }
-
-            self.write(out_buf.as_slice())?;
-        }
-
-        self.write(b"\r\n.\r\n")?;
-        self.read_response()
-    }
-
-    /// Sends an SMTP command
-    pub fn command<C: Display>(&mut self, command: C) -> SmtpResult {
-        self.write(command.to_string().as_bytes())?;
-        self.read_response()
-    }
-
-    /// Writes a string to the server
-    fn write(&mut self, string: &[u8]) -> Result<(), Error> {
-        if self.stream.is_none() {
-            return Err(From::from("Connection closed"));
-        }
-
-        self.stream.as_mut().unwrap().write_all(string)?;
-        self.stream.as_mut().unwrap().flush()?;
-
-        debug!(
-            "Wrote: {}",
-            escape_crlf(String::from_utf8_lossy(string).as_ref())
-        );
-        Ok(())
-    }
-
-    /// Gets the SMTP response
-    fn read_response(&mut self) -> SmtpResult {
-        let mut raw_response = String::new();
-        let mut response = raw_response.parse::<Response>();
-
-        while response.is_err() {
-            if response.as_ref().err().unwrap() != &NomErrorKind::Complete {
-                break;
-            }
-            // TODO read more than one line
-            let read_count = self.stream.as_mut().unwrap().read_line(&mut raw_response)?;
-
-            // EOF is reached
-            if read_count == 0 {
-                break;
-            }
-
-            response = raw_response.parse::<Response>();
-        }
-
-        debug!("Read: {}", escape_crlf(raw_response.as_ref()));
-
-        let final_response = response?;
-
-        if final_response.is_positive() {
-            Ok(final_response)
-        } else {
-            Err(From::from(final_response))
-        }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::{escape_crlf, ClientCodec};
-
-    #[test]
-    fn test_codec() {
-        let mut codec = ClientCodec::new();
-        let mut buf: Vec<u8> = vec![];
-
-        assert!(codec.encode(b"test\r\n", &mut buf).is_ok());
-        assert!(codec.encode(b".\r\n", &mut buf).is_ok());
-        assert!(codec.encode(b"\r\ntest", &mut buf).is_ok());
-        assert!(codec.encode(b"te\r\n.\r\nst", &mut buf).is_ok());
-        assert!(codec.encode(b"test", &mut buf).is_ok());
-        assert!(codec.encode(b"test.", &mut buf).is_ok());
-        assert!(codec.encode(b"test\n", &mut buf).is_ok());
-        assert!(codec.encode(b".test\n", &mut buf).is_ok());
-        assert!(codec.encode(b"test", &mut buf).is_ok());
-        assert_eq!(
-            String::from_utf8(buf).unwrap(),
-            "test\r\n..\r\n\r\ntestte\r\n..\r\nsttesttest.test\n.test\ntest"
-        );
-    }
-
-    #[test]
-    fn test_escape_crlf() {
-        assert_eq!(escape_crlf("\r\n"), "<CRLF>");
-        assert_eq!(escape_crlf("EHLO my_name\r\n"), "EHLO my_name<CRLF>");
-        assert_eq!(
-            escape_crlf("EHLO my_name\r\nSIZE 42\r\n"),
-            "EHLO my_name<CRLF>SIZE 42<CRLF>"
-        );
-    }
-}

lettre/src/smtp/client/net.rs

@@ -1,172 +0,0 @@
-//! A trait to represent a stream
-
-use native_tls::{Protocol, TlsConnector, TlsStream};
-use smtp::client::mock::MockStream;
-use std::io::{self, ErrorKind, Read, Write};
-use std::net::{Ipv4Addr, Shutdown, SocketAddr, SocketAddrV4, TcpStream};
-use std::time::Duration;
-
-/// Parameters to use for secure clients
-#[derive(Clone)]
-#[allow(missing_debug_implementations)]
-pub struct ClientTlsParameters {
-    /// A connector from `native-tls`
-    pub connector: TlsConnector,
-    /// The domain to send during the TLS handshake
-    pub domain: String,
-}
-
-impl ClientTlsParameters {
-    /// Creates a `ClientTlsParameters`
-    pub fn new(domain: String, connector: TlsConnector) -> ClientTlsParameters {
-        ClientTlsParameters { connector, domain }
-    }
-}
-
-/// Accepted protocols by default.
-/// This removes TLS 1.0 and 1.1 compared to tls-native defaults.
-pub const DEFAULT_TLS_PROTOCOLS: &[Protocol] = &[Protocol::Tlsv12];
-
-#[derive(Debug)]
-/// Represents the different types of underlying network streams
-pub enum NetworkStream {
-    /// Plain TCP stream
-    Tcp(TcpStream),
-    /// Encrypted TCP stream
-    Tls(TlsStream<TcpStream>),
-    /// Mock stream
-    Mock(MockStream),
-}
-
-impl NetworkStream {
-    /// Returns peer's address
-    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-        match *self {
-            NetworkStream::Tcp(ref s) => s.peer_addr(),
-            NetworkStream::Tls(ref s) => s.get_ref().peer_addr(),
-            NetworkStream::Mock(_) => Ok(SocketAddr::V4(SocketAddrV4::new(
-                Ipv4Addr::new(127, 0, 0, 1),
-                80,
-            ))),
-        }
-    }
-
-    /// Shutdowns the connection
-    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
-        match *self {
-            NetworkStream::Tcp(ref s) => s.shutdown(how),
-            NetworkStream::Tls(ref s) => s.get_ref().shutdown(how),
-            NetworkStream::Mock(_) => Ok(()),
-        }
-    }
-}
-
-impl Read for NetworkStream {
-    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        match *self {
-            NetworkStream::Tcp(ref mut s) => s.read(buf),
-            NetworkStream::Tls(ref mut s) => s.read(buf),
-            NetworkStream::Mock(ref mut s) => s.read(buf),
-        }
-    }
-}
-
-impl Write for NetworkStream {
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        match *self {
-            NetworkStream::Tcp(ref mut s) => s.write(buf),
-            NetworkStream::Tls(ref mut s) => s.write(buf),
-            NetworkStream::Mock(ref mut s) => s.write(buf),
-        }
-    }
-
-    fn flush(&mut self) -> io::Result<()> {
-        match *self {
-            NetworkStream::Tcp(ref mut s) => s.flush(),
-            NetworkStream::Tls(ref mut s) => s.flush(),
-            NetworkStream::Mock(ref mut s) => s.flush(),
-        }
-    }
-}
-
-/// A trait for the concept of opening a stream
-pub trait Connector: Sized {
-    /// Opens a connection to the given IP socket
-    fn connect(addr: &SocketAddr, tls_parameters: Option<&ClientTlsParameters>)
-        -> io::Result<Self>;
-    /// Upgrades to TLS connection
-    fn upgrade_tls(&mut self, tls_parameters: &ClientTlsParameters) -> io::Result<()>;
-    /// Is the NetworkStream encrypted
-    fn is_encrypted(&self) -> bool;
-}
-
-impl Connector for NetworkStream {
-    fn connect(
-        addr: &SocketAddr,
-        tls_parameters: Option<&ClientTlsParameters>,
-    ) -> io::Result<NetworkStream> {
-        let tcp_stream = TcpStream::connect(addr)?;
-
-        match tls_parameters {
-            Some(context) => context
-                .connector
-                .connect(context.domain.as_ref(), tcp_stream)
-                .map(NetworkStream::Tls)
-                .map_err(|e| io::Error::new(ErrorKind::Other, e)),
-            None => Ok(NetworkStream::Tcp(tcp_stream)),
-        }
-    }
-
-    #[cfg_attr(feature = "cargo-clippy", allow(clippy::match_same_arms))]
-    fn upgrade_tls(&mut self, tls_parameters: &ClientTlsParameters) -> io::Result<()> {
-        *self = match *self {
-            NetworkStream::Tcp(ref mut stream) => match tls_parameters
-                .connector
-                .connect(tls_parameters.domain.as_ref(), stream.try_clone().unwrap())
-            {
-                Ok(tls_stream) => NetworkStream::Tls(tls_stream),
-                Err(err) => return Err(io::Error::new(ErrorKind::Other, err)),
-            },
-            NetworkStream::Tls(_) => return Ok(()),
-            NetworkStream::Mock(_) => return Ok(()),
-        };
-
-        Ok(())
-    }
-
-    #[cfg_attr(feature = "cargo-clippy", allow(clippy::match_same_arms))]
-    fn is_encrypted(&self) -> bool {
-        match *self {
-            NetworkStream::Tcp(_) => false,
-            NetworkStream::Tls(_) => true,
-            NetworkStream::Mock(_) => false,
-        }
-    }
-}
-
-/// A trait for read and write timeout support
-pub trait Timeout: Sized {
-    /// Set read timeout for IO calls
-    fn set_read_timeout(&mut self, duration: Option<Duration>) -> io::Result<()>;
-    /// Set write timeout for IO calls
-    fn set_write_timeout(&mut self, duration: Option<Duration>) -> io::Result<()>;
-}
-
-impl Timeout for NetworkStream {
-    fn set_read_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
-        match *self {
-            NetworkStream::Tcp(ref mut stream) => stream.set_read_timeout(duration),
-            NetworkStream::Tls(ref mut stream) => stream.get_ref().set_read_timeout(duration),
-            NetworkStream::Mock(_) => Ok(()),
-        }
-    }
-
-    /// Set write timeout for IO calls
-    fn set_write_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
-        match *self {
-            NetworkStream::Tcp(ref mut stream) => stream.set_write_timeout(duration),
-            NetworkStream::Tls(ref mut stream) => stream.get_ref().set_write_timeout(duration),
-            NetworkStream::Mock(_) => Ok(()),
-        }
-    }
-}

lettre/src/smtp/error.rs

@@ -1,132 +0,0 @@
-//! Error and result type for SMTP clients
-
-use self::Error::*;
-use base64::DecodeError;
-use native_tls;
-use nom;
-use smtp::response::{Response, Severity};
-use std::error::Error as StdError;
-use std::fmt;
-use std::fmt::{Display, Formatter};
-use std::io;
-use std::string::FromUtf8Error;
-
-/// An enum of all error kinds.
-#[derive(Debug)]
-pub enum Error {
-    /// Transient SMTP error, 4xx reply code
-    ///
-    /// [RFC 5321, section 4.2.1](https://tools.ietf.org/html/rfc5321#section-4.2.1)
-    Transient(Response),
-    /// Permanent SMTP error, 5xx reply code
-    ///
-    /// [RFC 5321, section 4.2.1](https://tools.ietf.org/html/rfc5321#section-4.2.1)
-    Permanent(Response),
-    /// Error parsing a response
-    ResponseParsing(&'static str),
-    /// Error parsing a base64 string in response
-    ChallengeParsing(DecodeError),
-    /// Error parsing UTF8in response
-    Utf8Parsing(FromUtf8Error),
-    /// Internal client error
-    Client(&'static str),
-    /// DNS resolution error
-    Resolution,
-    /// IO error
-    Io(io::Error),
-    /// TLS error
-    Tls(native_tls::Error),
-    /// Parsing error
-    Parsing(nom::ErrorKind),
-}
-
-impl Display for Error {
-    fn fmt(&self, fmt: &mut Formatter) -> Result<(), fmt::Error> {
-        fmt.write_str(self.description())
-    }
-}
-
-impl StdError for Error {
-    #[cfg_attr(feature = "cargo-clippy", allow(clippy::match_same_arms))]
-    fn description(&self) -> &str {
-        match *self {
-            // Try to display the first line of the server's response that usually
-            // contains a short humanly readable error message
-            Transient(ref err) => match err.first_line() {
-                Some(line) => line,
-                None => "undetailed transient error during SMTP transaction",
-            },
-            Permanent(ref err) => match err.first_line() {
-                Some(line) => line,
-                None => "undetailed permanent error during SMTP transaction",
-            },
-            ResponseParsing(err) => err,
-            ChallengeParsing(ref err) => err.description(),
-            Utf8Parsing(ref err) => err.description(),
-            Resolution => "could not resolve hostname",
-            Client(err) => err,
-            Io(ref err) => err.description(),
-            Tls(ref err) => err.description(),
-            Parsing(ref err) => err.description(),
-        }
-    }
-
-    fn cause(&self) -> Option<&StdError> {
-        match *self {
-            ChallengeParsing(ref err) => Some(&*err),
-            Utf8Parsing(ref err) => Some(&*err),
-            Io(ref err) => Some(&*err),
-            Tls(ref err) => Some(&*err),
-            _ => None,
-        }
-    }
-}
-
-impl From<io::Error> for Error {
-    fn from(err: io::Error) -> Error {
-        Io(err)
-    }
-}
-
-impl From<native_tls::Error> for Error {
-    fn from(err: native_tls::Error) -> Error {
-        Tls(err)
-    }
-}
-
-impl From<nom::ErrorKind> for Error {
-    fn from(err: nom::ErrorKind) -> Error {
-        Parsing(err)
-    }
-}
-
-impl From<DecodeError> for Error {
-    fn from(err: DecodeError) -> Error {
-        ChallengeParsing(err)
-    }
-}
-
-impl From<FromUtf8Error> for Error {
-    fn from(err: FromUtf8Error) -> Error {
-        Utf8Parsing(err)
-    }
-}
-
-impl From<Response> for Error {
-    fn from(response: Response) -> Error {
-        match response.code.severity {
-            Severity::TransientNegativeCompletion => Transient(response),
-            Severity::PermanentNegativeCompletion => Permanent(response),
-            _ => Client("Unknown error code"),
-        }
-    }
-}
-
-impl From<&'static str> for Error {
-    fn from(string: &'static str) -> Error {
-        Client(string)
-    }
-}
-
-/// SMTP result type
-pub type SmtpResult = Result<Response, Error>;

lettre/src/smtp/mod.rs

@@ -1,479 +0,0 @@
-//! The SMTP transport sends emails using the SMTP protocol.
-//!
-//! This SMTP client follows [RFC
-//! 5321](https://tools.ietf.org/html/rfc5321), and is designed to efficiently send emails from an
-//! application to a relay email server, as it relies as much as possible on the relay server
-//! for sanity and RFC compliance checks.
-//!
-//! It implements the following extensions:
-//!
-//! * 8BITMIME ([RFC 6152](https://tools.ietf.org/html/rfc6152))
-//! * AUTH ([RFC 4954](http://tools.ietf.org/html/rfc4954)) with PLAIN, LOGIN and XOAUTH2 mechanisms
-//! * STARTTLS ([RFC 2487](http://tools.ietf.org/html/rfc2487))
-//! * SMTPUTF8 ([RFC 6531](http://tools.ietf.org/html/rfc6531))
-//!
-
-use native_tls::TlsConnector;
-use smtp::authentication::{
-    Credentials, Mechanism, DEFAULT_ENCRYPTED_MECHANISMS, DEFAULT_UNENCRYPTED_MECHANISMS,
-};
-use smtp::client::net::ClientTlsParameters;
-use smtp::client::net::DEFAULT_TLS_PROTOCOLS;
-use smtp::client::InnerClient;
-use smtp::commands::*;
-use smtp::error::{Error, SmtpResult};
-use smtp::extension::{ClientId, Extension, MailBodyParameter, MailParameter, ServerInfo};
-use std::net::{SocketAddr, ToSocketAddrs};
-use std::time::Duration;
-use {SendableEmail, Transport};
-
-pub mod authentication;
-pub mod client;
-pub mod commands;
-pub mod error;
-pub mod extension;
-#[cfg(feature = "connection-pool")]
-pub mod r2d2;
-pub mod response;
-pub mod util;
-
-// Registered port numbers:
-// https://www.iana.
-// org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml
-
-/// Default smtp port
-pub const SMTP_PORT: u16 = 25;
-/// Default submission port
-pub const SUBMISSION_PORT: u16 = 587;
-/// Default submission over TLS port
-pub const SUBMISSIONS_PORT: u16 = 465;
-
-/// How to apply TLS to a client connection
-#[derive(Clone)]
-#[allow(missing_debug_implementations)]
-pub enum ClientSecurity {
-    /// Insecure connection only (for testing purposes)
-    None,
-    /// Start with insecure connection and use `STARTTLS` when available
-    Opportunistic(ClientTlsParameters),
-    /// Start with insecure connection and require `STARTTLS`
-    Required(ClientTlsParameters),
-    /// Use TLS wrapped connection
-    Wrapper(ClientTlsParameters),
-}
-
-/// Configures connection reuse behavior
-#[derive(Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub enum ConnectionReuseParameters {
-    /// Unlimited connection reuse
-    ReuseUnlimited,
-    /// Maximum number of connection reuse
-    ReuseLimited(u16),
-    /// Disable connection reuse, close connection after each transaction
-    NoReuse,
-}
-
-/// Contains client configuration
-#[allow(missing_debug_implementations)]
-#[derive(Clone)]
-pub struct SmtpClient {
-    /// Enable connection reuse
-    connection_reuse: ConnectionReuseParameters,
-    /// Name sent during EHLO
-    hello_name: ClientId,
-    /// Credentials
-    credentials: Option<Credentials>,
-    /// Socket we are connecting to
-    server_addr: SocketAddr,
-    /// TLS security configuration
-    security: ClientSecurity,
-    /// Enable UTF8 mailboxes in envelope or headers
-    smtp_utf8: bool,
-    /// Optional enforced authentication mechanism
-    authentication_mechanism: Option<Mechanism>,
-    /// Define network timeout
-    /// It can be changed later for specific needs (like a different timeout for each SMTP command)
-    timeout: Option<Duration>,
-}
-
-/// Builder for the SMTP `SmtpTransport`
-impl SmtpClient {
-    /// Creates a new SMTP client
-    ///
-    /// Defaults are:
-    ///
-    /// * No connection reuse
-    /// * No authentication
-    /// * No SMTPUTF8 support
-    /// * A 60 seconds timeout for smtp commands
-    ///
-    /// Consider using [`SmtpClient::new_simple`] instead, if possible.
-    pub fn new<A: ToSocketAddrs>(addr: A, security: ClientSecurity) -> Result<SmtpClient, Error> {
-        let mut addresses = addr.to_socket_addrs()?;
-
-        match addresses.next() {
-            Some(addr) => Ok(SmtpClient {
-                server_addr: addr,
-                security,
-                smtp_utf8: false,
-                credentials: None,
-                connection_reuse: ConnectionReuseParameters::NoReuse,
-                hello_name: ClientId::hostname(),
-                authentication_mechanism: None,
-                timeout: Some(Duration::new(60, 0)),
-            }),
-            None => Err(Error::Resolution),
-        }
-    }
-
-    /// Simple and secure transport, should be used when possible.
-    /// Creates an encrypted transport over submissions port, using the provided domain
-    /// to validate TLS certificates.
-    pub fn new_simple(domain: &str) -> Result<SmtpClient, Error> {
-        let mut tls_builder = TlsConnector::builder();
-        tls_builder.min_protocol_version(Some(DEFAULT_TLS_PROTOCOLS[0]));
-
-        let tls_parameters =
-            ClientTlsParameters::new(domain.to_string(), tls_builder.build().unwrap());
-
-        SmtpClient::new(
-            (domain, SUBMISSIONS_PORT),
-            ClientSecurity::Wrapper(tls_parameters),
-        )
-    }
-
-    /// Creates a new local SMTP client to port 25
-    pub fn new_unencrypted_localhost() -> Result<SmtpClient, Error> {
-        SmtpClient::new(("localhost", SMTP_PORT), ClientSecurity::None)
-    }
-
-    /// Enable SMTPUTF8 if the server supports it
-    pub fn smtp_utf8(mut self, enabled: bool) -> SmtpClient {
-        self.smtp_utf8 = enabled;
-        self
-    }
-
-    /// Set the name used during EHLO
-    pub fn hello_name(mut self, name: ClientId) -> SmtpClient {
-        self.hello_name = name;
-        self
-    }
-
-    /// Enable connection reuse
-    pub fn connection_reuse(mut self, parameters: ConnectionReuseParameters) -> SmtpClient {
-        self.connection_reuse = parameters;
-        self
-    }
-
-    /// Set the client credentials
-    pub fn credentials<S: Into<Credentials>>(mut self, credentials: S) -> SmtpClient {
-        self.credentials = Some(credentials.into());
-        self
-    }
-
-    /// Set the authentication mechanism to use
-    pub fn authentication_mechanism(mut self, mechanism: Mechanism) -> SmtpClient {
-        self.authentication_mechanism = Some(mechanism);
-        self
-    }
-
-    /// Set the timeout duration
-    pub fn timeout(mut self, timeout: Option<Duration>) -> SmtpClient {
-        self.timeout = timeout;
-        self
-    }
-
-    /// Build the SMTP client
-    ///
-    /// It does not connect to the server, but only creates the `SmtpTransport`
-    pub fn transport(self) -> SmtpTransport {
-        SmtpTransport::new(self)
-    }
-}
-
-/// Represents the state of a client
-#[derive(Debug)]
-struct State {
-    /// Panic state
-    pub panic: bool,
-    /// Connection reuse counter
-    pub connection_reuse_count: u16,
-}
-
-/// Structure that implements the high level SMTP client
-#[allow(missing_debug_implementations)]
-pub struct SmtpTransport {
-    /// Information about the server
-    /// Value is None before HELO/EHLO
-    server_info: Option<ServerInfo>,
-    /// SmtpTransport variable states
-    state: State,
-    /// Information about the client
-    client_info: SmtpClient,
-    /// Low level client
-    client: InnerClient,
-}
-
-macro_rules! try_smtp (
-    ($err: expr, $client: ident) => ({
-        match $err {
-            Ok(val) => val,
-            Err(err) => {
-                if !$client.state.panic {
-                    $client.state.panic = true;
-                    $client.close();
-                }
-                return Err(From::from(err))
-            },
-        }
-    })
-);
-
-impl<'a> SmtpTransport {
-    /// Creates a new SMTP client
-    ///
-    /// It does not connect to the server, but only creates the `SmtpTransport`
-    pub fn new(builder: SmtpClient) -> SmtpTransport {
-        let client = InnerClient::new();
-
-        SmtpTransport {
-            client,
-            server_info: None,
-            client_info: builder,
-            state: State {
-                panic: false,
-                connection_reuse_count: 0,
-            },
-        }
-    }
-
-    fn connect(&mut self) -> Result<(), Error> {
-        // Check if the connection is still available
-        if (self.state.connection_reuse_count > 0) && (!self.client.is_connected()) {
-            self.close();
-        }
-
-        if self.state.connection_reuse_count > 0 {
-            info!(
-                "connection already established to {}",
-                self.client_info.server_addr
-            );
-            return Ok(());
-        }
-
-        self.client.connect(
-            &self.client_info.server_addr,
-            match self.client_info.security {
-                ClientSecurity::Wrapper(ref tls_parameters) => Some(tls_parameters),
-                _ => None,
-            },
-        )?;
-
-        self.client.set_timeout(self.client_info.timeout)?;
-
-        // Log the connection
-        info!("connection established to {}", self.client_info.server_addr);
-
-        self.ehlo()?;
-
-        match (
-            &self.client_info.security.clone(),
-            self.server_info
-                .as_ref()
-                .unwrap()
-                .supports_feature(Extension::StartTls),
-        ) {
-            (&ClientSecurity::Required(_), false) => {
-                return Err(From::from("Could not encrypt connection, aborting"));
-            }
-            (&ClientSecurity::Opportunistic(_), false) => (),
-            (&ClientSecurity::None, _) => (),
-            (&ClientSecurity::Wrapper(_), _) => (),
-            (&ClientSecurity::Opportunistic(ref tls_parameters), true)
-            | (&ClientSecurity::Required(ref tls_parameters), true) => {
-                try_smtp!(self.client.command(StarttlsCommand), self);
-                try_smtp!(self.client.upgrade_tls_stream(tls_parameters), self);
-
-                debug!("connection encrypted");
-
-                // Send EHLO again
-                self.ehlo()?;
-            }
-        }
-
-        if self.client_info.credentials.is_some() {
-            let mut found = false;
-
-            // Compute accepted mechanism
-            let accepted_mechanisms = match self.client_info.authentication_mechanism {
-                Some(mechanism) => vec![mechanism],
-                None => {
-                    if self.client.is_encrypted() {
-                        DEFAULT_ENCRYPTED_MECHANISMS.to_vec()
-                    } else {
-                        DEFAULT_UNENCRYPTED_MECHANISMS.to_vec()
-                    }
-                }
-            };
-
-            for mechanism in accepted_mechanisms {
-                if self
-                    .server_info
-                    .as_ref()
-                    .unwrap()
-                    .supports_auth_mechanism(mechanism)
-                {
-                    found = true;
-                    try_smtp!(
-                        self.client
-                            .auth(mechanism, self.client_info.credentials.as_ref().unwrap(),),
-                        self
-                    );
-                    break;
-                }
-            }
-
-            if !found {
-                info!("No supported authentication mechanisms available");
-            }
-        }
-        Ok(())
-    }
-
-    /// Gets the EHLO response and updates server information
-    fn ehlo(&mut self) -> SmtpResult {
-        // Extended Hello
-        let ehlo_response = try_smtp!(
-            self.client.command(EhloCommand::new(ClientId::new(
-                self.client_info.hello_name.to_string()
-            ),)),
-            self
-        );
-
-        self.server_info = Some(try_smtp!(ServerInfo::from_response(&ehlo_response), self));
-
-        // Print server information
-        debug!("server {}", self.server_info.as_ref().unwrap());
-
-        Ok(ehlo_response)
-    }
-
-    /// Reset the client state
-    pub fn close(&mut self) {
-        // Close the SMTP transaction if needed
-        self.client.close();
-
-        // Reset the client state
-        self.server_info = None;
-        self.state.panic = false;
-        self.state.connection_reuse_count = 0;
-    }
-}
-
-impl<'a> Transport<'a> for SmtpTransport {
-    type Result = SmtpResult;
-
-    /// Sends an email
-    #[cfg_attr(
-        feature = "cargo-clippy",
-        allow(clippy::match_same_arms, clippy::cyclomatic_complexity)
-    )]
-    fn send(&mut self, email: SendableEmail) -> SmtpResult {
-        let message_id = email.message_id().to_string();
-
-        if !self.client.is_connected() {
-            self.connect()?;
-        }
-
-        // Mail
-        let mut mail_options = vec![];
-
-        if self
-            .server_info
-            .as_ref()
-            .unwrap()
-            .supports_feature(Extension::EightBitMime)
-        {
-            mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
-        }
-
-        if self
-            .server_info
-            .as_ref()
-            .unwrap()
-            .supports_feature(Extension::SmtpUtfEight)
-            && self.client_info.smtp_utf8
-        {
-            mail_options.push(MailParameter::SmtpUtfEight);
-        }
-
-        try_smtp!(
-            self.client.command(MailCommand::new(
-                email.envelope().from().cloned(),
-                mail_options,
-            )),
-            self
-        );
-
-        // Log the mail command
-        info!(
-            "{}: from=<{}>",
-            message_id,
-            match email.envelope().from() {
-                Some(address) => address.to_string(),
-                None => "".to_string(),
-            }
-        );
-
-        // Recipient
-        for to_address in email.envelope().to() {
-            try_smtp!(
-                self.client
-                    .command(RcptCommand::new(to_address.clone(), vec![])),
-                self
-            );
-            // Log the rcpt command
-            info!("{}: to=<{}>", message_id, to_address);
-        }
-
-        // Data
-        try_smtp!(self.client.command(DataCommand), self);
-
-        // Message content
-        let result = self.client.message(Box::new(email.message()));
-
-        if result.is_ok() {
-            // Increment the connection reuse counter
-            self.state.connection_reuse_count += 1;
-
-            // Log the message
-            info!(
-                "{}: conn_use={}, status=sent ({})",
-                message_id,
-                self.state.connection_reuse_count,
-                result
-                    .as_ref()
-                    .ok()
-                    .unwrap()
-                    .message
-                    .iter()
-                    .next()
-                    .unwrap_or(&"no response".to_string())
-            );
-        }
-
-        // Test if we can reuse the existing connection
-        match self.client_info.connection_reuse {
-            ConnectionReuseParameters::ReuseLimited(limit)
-                if self.state.connection_reuse_count >= limit =>
-            {
-                self.close()
-            }
-            ConnectionReuseParameters::NoReuse => self.close(),
-            _ => (),
-        }
-
-        result
-    }
-}

lettre/src/smtp/r2d2.rs

@@ -1,38 +0,0 @@
-use r2d2::ManageConnection;
-use smtp::error::Error;
-use smtp::{ConnectionReuseParameters, SmtpClient, SmtpTransport};
-
-pub struct SmtpConnectionManager {
-    transport_builder: SmtpClient,
-}
-
-impl SmtpConnectionManager {
-    pub fn new(transport_builder: SmtpClient) -> Result<SmtpConnectionManager, Error> {
-        Ok(SmtpConnectionManager {
-            transport_builder: transport_builder
-                .connection_reuse(ConnectionReuseParameters::ReuseUnlimited),
-        })
-    }
-}
-
-impl ManageConnection for SmtpConnectionManager {
-    type Connection = SmtpTransport;
-    type Error = Error;
-
-    fn connect(&self) -> Result<Self::Connection, Error> {
-        let mut transport = SmtpTransport::new(self.transport_builder.clone());
-        transport.connect()?;
-        Ok(transport)
-    }
-
-    fn is_valid(&self, conn: &mut Self::Connection) -> Result<(), Error> {
-        if conn.client.is_connected() {
-            return Ok(());
-        }
-        Err(Error::Client("is not connected anymore"))
-    }
-
-    fn has_broken(&self, conn: &mut Self::Connection) -> bool {
-        conn.state.panic
-    }
-}

lettre/src/stub/mod.rs

@@ -1,44 +0,0 @@
-//! The stub transport only logs message envelope and drops the content. It can be useful for
-//! testing purposes.
-//!
-
-use SendableEmail;
-use Transport;
-
-/// This transport logs the message envelope and returns the given response
-#[derive(Debug, Clone, Copy)]
-pub struct StubTransport {
-    response: StubResult,
-}
-
-impl StubTransport {
-    /// Creates a new transport that always returns the given response
-    pub fn new(response: StubResult) -> StubTransport {
-        StubTransport { response }
-    }
-
-    /// Creates a new transport that always returns a success response
-    pub fn new_positive() -> StubTransport {
-        StubTransport { response: Ok(()) }
-    }
-}
-
-/// SMTP result type
-pub type StubResult = Result<(), ()>;
-
-impl<'a> Transport<'a> for StubTransport {
-    type Result = StubResult;
-
-    fn send(&mut self, email: SendableEmail) -> StubResult {
-        info!(
-            "{}: from=<{}> to=<{:?}>",
-            email.message_id(),
-            match email.envelope().from() {
-                Some(address) => address.to_string(),
-                None => "".to_string(),
-            },
-            email.envelope().to()
-        );
-        self.response
-    }
-}

lettre/tests/r2d2_smtp.rs

@@ -1,74 +0,0 @@
-#[cfg(all(test, feature = "smtp-transport", feature = "connection-pool"))]
-mod test {
-    extern crate lettre;
-    extern crate r2d2;
-
-    use self::lettre::{ClientSecurity, EmailAddress, Envelope, SendableEmail, SmtpClient};
-    use self::lettre::{SmtpConnectionManager, Transport};
-    use self::r2d2::Pool;
-    use std::sync::mpsc;
-    use std::thread;
-
-    fn email(message: &str) -> SendableEmail {
-        SendableEmail::new(
-            Envelope::new(
-                Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-                vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-            )
-            .unwrap(),
-            "id".to_string(),
-            message.to_string().into_bytes(),
-        )
-    }
-
-    #[test]
-    fn send_one() {
-        let client = SmtpClient::new("localhost:2525", ClientSecurity::None).unwrap();
-        let manager = SmtpConnectionManager::new(client).unwrap();
-        let pool = Pool::builder().max_size(1).build(manager).unwrap();
-
-        let mut mailer = pool.get().unwrap();
-        let result = (*mailer).send(email("send one"));
-        assert!(result.is_ok());
-    }
-
-    #[test]
-    fn send_from_thread() {
-        let client = SmtpClient::new("127.0.0.1:2525", ClientSecurity::None).unwrap();
-        let manager = SmtpConnectionManager::new(client).unwrap();
-        let pool = Pool::builder().max_size(2).build(manager).unwrap();
-
-        let (s1, r1) = mpsc::channel();
-        let (s2, r2) = mpsc::channel();
-
-        let pool1 = pool.clone();
-        let t1 = thread::spawn(move || {
-            let mut conn = pool1.get().unwrap();
-            s1.send(()).unwrap();
-            r2.recv().unwrap();
-            (*conn)
-                .send(email("send from thread 1"))
-                .expect("Send failed from thread 1");
-            drop(conn);
-        });
-
-        let pool2 = pool.clone();
-        let t2 = thread::spawn(move || {
-            let mut conn = pool2.get().unwrap();
-            s2.send(()).unwrap();
-            r1.recv().unwrap();
-            (*conn)
-                .send(email("send from thread 2"))
-                .expect("Send failed from thread 2");
-            drop(conn);
-        });
-
-        t1.join().unwrap();
-        t2.join().unwrap();
-
-        let mut mailer = pool.get().unwrap();
-        (*mailer)
-            .send(email("send from main thread"))
-            .expect("Send failed from main thread");
-    }
-}

lettre/tests/skeptic.rs

@@ -1,65 +0,0 @@
-extern crate glob;
-
-use self::glob::glob;
-use std::env;
-use std::env::consts::EXE_EXTENSION;
-use std::path::Path;
-use std::process::Command;
-
-/*
-#[test]
-fn test_readme() {
-    let readme = Path::new(file!())
-        .parent()
-        .unwrap()
-        .parent()
-        .unwrap()
-        .parent()
-        .unwrap()
-        .join("README.md");
-
-    skeptic_test(&readme);
-}
-*/
-
-#[test]
-fn book_test() {
-    let mut book_path = env::current_dir().unwrap();
-    book_path.push(
-        Path::new(file!())
-            .parent()
-            .unwrap()
-            .parent()
-            .unwrap()
-            .parent()
-            .unwrap()
-            .join("../website/content/sending-messages"),
-    ); // For some reasons, calling .parent() once more gives us None...
-
-    for md in glob(&format!("{}/*.md", book_path.to_str().unwrap())).unwrap() {
-        skeptic_test(&md.unwrap());
-    }
-}
-
-fn skeptic_test(path: &Path) {
-    let rustdoc = Path::new("rustdoc").with_extension(EXE_EXTENSION);
-    let exe = env::current_exe().unwrap();
-    let depdir = exe.parent().unwrap();
-
-    let mut cmd = Command::new(rustdoc);
-    cmd.args(&["--verbose", "--test"])
-        .arg("-L")
-        .arg(&depdir)
-        .arg(path);
-
-    let result = cmd
-        .spawn()
-        .expect("Failed to spawn process")
-        .wait()
-        .expect("Failed to run process");
-
-    assert!(
-        result.success(),
-        format!("Failed to run rustdoc tests on {:?}", path)
-    );
-}

lettre/tests/transport_file.rs

@@ -1,44 +0,0 @@
-extern crate lettre;
-
-#[cfg(test)]
-#[cfg(feature = "file-transport")]
-mod test {
-
-    use lettre::file::FileTransport;
-    use lettre::{EmailAddress, Envelope, SendableEmail, Transport};
-    use std::env::temp_dir;
-    use std::fs::remove_file;
-    use std::fs::File;
-    use std::io::Read;
-
-    #[test]
-    fn file_transport() {
-        let mut sender = FileTransport::new(temp_dir());
-        let email = SendableEmail::new(
-            Envelope::new(
-                Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-                vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-            )
-            .unwrap(),
-            "id".to_string(),
-            "Hello ß☺ example".to_string().into_bytes(),
-        );
-        let message_id = email.message_id().to_string();
-
-        let result = sender.send(email);
-        assert!(result.is_ok());
-
-        let file = format!("{}/{}.json", temp_dir().to_str().unwrap(), message_id);
-        let mut f = File::open(file.clone()).unwrap();
-        let mut buffer = String::new();
-        let _ = f.read_to_string(&mut buffer);
-
-        assert_eq!(
-            buffer,
-            "{\"envelope\":{\"forward_path\":[\"root@localhost\"],\"reverse_path\":\"user@localhost\"},\"message_id\":\"id\",\"message\":[72,101,108,108,111,32,195,159,226,152,186,32,101,120,97,109,112,108,101]}"
-        );
-
-        remove_file(file).unwrap();
-    }
-
-}

lettre/tests/transport_sendmail.rs

@@ -1,27 +0,0 @@
-extern crate lettre;
-
-#[cfg(test)]
-#[cfg(feature = "sendmail-transport")]
-mod test {
-    use lettre::sendmail::SendmailTransport;
-    use lettre::{EmailAddress, Envelope, SendableEmail, Transport};
-
-    #[test]
-    fn sendmail_transport_simple() {
-        let mut sender = SendmailTransport::new();
-        let email = SendableEmail::new(
-            Envelope::new(
-                Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-                vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-            )
-            .unwrap(),
-            "id".to_string(),
-            "Hello ß☺ example".to_string().into_bytes(),
-        );
-
-        let result = sender.send(email);
-        println!("{:?}", result);
-        assert!(result.is_ok());
-    }
-
-}

lettre/tests/transport_smtp.rs

@@ -1,27 +0,0 @@
-extern crate lettre;
-
-#[cfg(test)]
-#[cfg(feature = "smtp-transport")]
-mod test {
-    use lettre::{ClientSecurity, EmailAddress, Envelope, SendableEmail, SmtpClient, Transport};
-
-    #[test]
-    fn smtp_transport_simple() {
-        let email = SendableEmail::new(
-            Envelope::new(
-                Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-                vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-            )
-            .unwrap(),
-            "id".to_string(),
-            "Hello ß☺ example".to_string().into_bytes(),
-        );
-
-        SmtpClient::new("127.0.0.1:2525", ClientSecurity::None)
-            .unwrap()
-            .transport()
-            .send(email)
-            .unwrap();
-    }
-
-}

lettre/tests/transport_stub.rs

@@ -1,31 +0,0 @@
-extern crate lettre;
-
-use lettre::stub::StubTransport;
-use lettre::{EmailAddress, Envelope, SendableEmail, Transport};
-
-#[test]
-fn stub_transport() {
-    let mut sender_ok = StubTransport::new_positive();
-    let mut sender_ko = StubTransport::new(Err(()));
-    let email_ok = SendableEmail::new(
-        Envelope::new(
-            Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-            vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-        )
-        .unwrap(),
-        "id".to_string(),
-        "Hello ß☺ example".to_string().into_bytes(),
-    );
-    let email_ko = SendableEmail::new(
-        Envelope::new(
-            Some(EmailAddress::new("user@localhost".to_string()).unwrap()),
-            vec![EmailAddress::new("root@localhost".to_string()).unwrap()],
-        )
-        .unwrap(),
-        "id".to_string(),
-        "Hello ß☺ example".to_string().into_bytes(),
-    );
-
-    sender_ok.send(email_ok).unwrap();
-    sender_ko.send(email_ko).unwrap_err();
-}

lettre_email/CHANGELOG.md

@@ -1 +0,0 @@
-../CHANGELOG.md

lettre_email/Cargo.toml

@@ -1,33 +0,0 @@
-[package]
-
-name = "lettre_email"
-version = "0.9.0" # remember to update html_root_url
-description = "Email builder"
-readme = "README.md"
-homepage = "http://lettre.at"
-repository = "https://github.com/lettre/lettre"
-license = "MIT"
-authors = ["Alexis Mousset <contact@amousset.me>"]
-categories = ["email"]
-keywords = ["email", "mailer"]
-
-[badges]
-travis-ci = { repository = "lettre/lettre_email" }
-appveyor = { repository = "lettre/lettre_email" }
-maintenance = { status = "actively-developed" }
-is-it-maintained-issue-resolution = { repository = "lettre/lettre_email" }
-is-it-maintained-open-issues = { repository = "lettre/lettre_email" }
-
-[dev-dependencies]
-lettre = { version = "^0.9", path = "../lettre", features = ["smtp-transport"] }
-glob = "0.3"
-
-[dependencies]
-email = "^0.0.20"
-mime = "^0.3"
-time = "^0.1"
-uuid = { version = "^0.7", features = ["v4"] }
-lettre = { version = "^0.9", path = "../lettre", default-features = false }
-base64 = "^0.10"
-failure = "^0.1"
-failure_derive = "^0.1"

lettre_email/LICENSE

@@ -1 +0,0 @@
-../LICENSE

lettre_email/README.md

@@ -1 +0,0 @@
-../README.md

lettre_email/examples/local.rs

@@ -1,34 +0,0 @@
-extern crate lettre;
-extern crate lettre_email;
-extern crate mime;
-
-use lettre::{SmtpClient, Transport};
-use lettre_email::Email;
-use std::path::Path;
-
-fn main() {
-    let email = Email::builder()
-        // Addresses can be specified by the tuple (email, alias)
-        .to(("user@example.org", "Firstname Lastname"))
-        // ... or by an address only
-        .from("user@example.com")
-        .subject("Hi, Hello world")
-        .text("Hello world.")
-        .attachment_from_file(Path::new("Cargo.toml"), None, &mime::TEXT_PLAIN)
-        .unwrap()
-        .build()
-        .unwrap();
-
-    // Open a local connection on port 25
-    let mut mailer = SmtpClient::new_unencrypted_localhost().unwrap().transport();
-    // Send the email
-    let result = mailer.send(email.into());
-
-    if result.is_ok() {
-        println!("Email sent");
-    } else {
-        println!("Could not send email: {:?}", result);
-    }
-
-    assert!(result.is_ok());
-}

lettre_email/src/error.rs

@@ -1,36 +0,0 @@
-//! Error and result type for emails
-
-use lettre;
-use std::io;
-
-/// An enum of all error kinds.
-#[derive(Debug, Fail)]
-pub enum Error {
-    /// Envelope error
-    #[fail(display = "lettre error: {}", error)]
-    Envelope {
-        /// inner error
-        error: lettre::error::Error,
-    },
-    /// Unparseable filename for attachment
-    #[fail(display = "the attachment filename could not be parsed")]
-    CannotParseFilename,
-    /// IO error
-    #[fail(display = "IO error: {}", error)]
-    Io {
-        /// inner error
-        error: io::Error,
-    },
-}
-
-impl From<io::Error> for Error {
-    fn from(err: io::Error) -> Error {
-        Error::Io { error: err }
-    }
-}
-
-impl From<lettre::error::Error> for Error {
-    fn from(err: lettre::error::Error) -> Error {
-        Error::Envelope { error: err }
-    }
-}

lettre_email/src/lib.rs

@@ -1,606 +0,0 @@
-//! Lettre is a mailer written in Rust. lettre_email provides a simple email builder.
-//!
-
-#![doc(html_root_url = "https://docs.rs/lettre_email/0.9.0")]
-#![deny(
-    missing_docs,
-    missing_debug_implementations,
-    missing_copy_implementations,
-    trivial_casts,
-    trivial_numeric_casts,
-    unsafe_code,
-    unstable_features,
-    unused_import_braces
-)]
-
-extern crate failure;
-#[macro_use]
-extern crate failure_derive;
-
-extern crate base64;
-extern crate email as email_format;
-extern crate lettre;
-extern crate mime;
-extern crate time;
-extern crate uuid;
-
-pub mod error;
-
-pub use email_format::{Address, Header, Mailbox, MimeMessage, MimeMultipartType};
-use error::Error as EmailError;
-use failure::Error;
-use lettre::{error::Error as LettreError, EmailAddress, Envelope, SendableEmail};
-use mime::Mime;
-use std::fs;
-use std::path::Path;
-use std::str::FromStr;
-use time::{now, Tm};
-use uuid::Uuid;
-
-/// Builds a `MimeMessage` structure
-#[derive(PartialEq, Eq, Clone, Debug)]
-pub struct PartBuilder {
-    /// Message
-    message: MimeMessage,
-}
-
-impl Default for PartBuilder {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-/// Represents a message id
-pub type MessageId = String;
-
-/// Builds an `Email` structure
-#[derive(PartialEq, Eq, Clone, Debug, Default)]
-pub struct EmailBuilder {
-    /// Message
-    message: PartBuilder,
-    /// The recipients' addresses for the mail header
-    to: Vec<Address>,
-    /// The sender addresses for the mail header
-    from: Vec<Address>,
-    /// The Cc addresses for the mail header
-    cc: Vec<Address>,
-    /// The Bcc addresses for the mail header
-    bcc: Vec<Address>,
-    /// The Reply-To addresses for the mail header
-    reply_to: Vec<Address>,
-    /// The In-Reply-To ids for the mail header
-    in_reply_to: Vec<MessageId>,
-    /// The References ids for the mail header
-    references: Vec<MessageId>,
-    /// The sender address for the mail header
-    sender: Option<Mailbox>,
-    /// The envelope
-    envelope: Option<Envelope>,
-    /// Date issued
-    date_issued: bool,
-}
-
-/// Simple email representation
-#[derive(PartialEq, Eq, Clone, Debug)]
-pub struct Email {
-    /// Message
-    message: Vec<u8>,
-    /// Envelope
-    envelope: Envelope,
-    /// Message-ID
-    message_id: Uuid,
-}
-
-impl Into<SendableEmail> for Email {
-    fn into(self) -> SendableEmail {
-        SendableEmail::new(
-            self.envelope.clone(),
-            self.message_id.to_string(),
-            self.message,
-        )
-    }
-}
-
-impl Email {
-    /// TODO
-    pub fn builder() -> EmailBuilder {
-        EmailBuilder::new()
-    }
-}
-
-impl PartBuilder {
-    /// Creates a new empty part
-    pub fn new() -> PartBuilder {
-        PartBuilder {
-            message: MimeMessage::new_blank_message(),
-        }
-    }
-
-    /// Adds a generic header
-    pub fn header<A: Into<Header>>(mut self, header: A) -> PartBuilder {
-        self.message.headers.insert(header.into());
-        self
-    }
-
-    /// Sets the body
-    pub fn body<S: Into<String>>(mut self, body: S) -> PartBuilder {
-        self.message.body = body.into();
-        self
-    }
-
-    /// Defines a `MimeMultipartType` value
-    pub fn message_type(mut self, mime_type: MimeMultipartType) -> PartBuilder {
-        self.message.message_type = Some(mime_type);
-        self
-    }
-
-    /// Adds a `ContentType` header with the given MIME type
-    pub fn content_type(self, content_type: &Mime) -> PartBuilder {
-        self.header(("Content-Type", format!("{}", content_type).as_ref()))
-    }
-
-    /// Adds a child part
-    pub fn child(mut self, child: MimeMessage) -> PartBuilder {
-        self.message.children.push(child);
-        self
-    }
-
-    /// Gets built `MimeMessage`
-    pub fn build(mut self) -> MimeMessage {
-        self.message.update_headers();
-        self.message
-    }
-}
-
-impl EmailBuilder {
-    /// Creates a new empty email
-    pub fn new() -> EmailBuilder {
-        EmailBuilder {
-            message: PartBuilder::new(),
-            to: vec![],
-            from: vec![],
-            cc: vec![],
-            bcc: vec![],
-            reply_to: vec![],
-            in_reply_to: vec![],
-            references: vec![],
-            sender: None,
-            envelope: None,
-            date_issued: false,
-        }
-    }
-
-    /// Sets the email body
-    pub fn body<S: Into<String>>(mut self, body: S) -> EmailBuilder {
-        self.message = self.message.body(body);
-        self
-    }
-
-    /// Add a generic header
-    pub fn header<A: Into<Header>>(mut self, header: A) -> EmailBuilder {
-        self.message = self.message.header(header);
-        self
-    }
-
-    /// Adds a `From` header and stores the sender address
-    pub fn from<A: Into<Mailbox>>(mut self, address: A) -> EmailBuilder {
-        let mailbox = address.into();
-        self.from.push(Address::Mailbox(mailbox));
-        self
-    }
-
-    /// Adds a `To` header and stores the recipient address
-    pub fn to<A: Into<Mailbox>>(mut self, address: A) -> EmailBuilder {
-        let mailbox = address.into();
-        self.to.push(Address::Mailbox(mailbox));
-        self
-    }
-
-    /// Adds a `Cc` header and stores the recipient address
-    pub fn cc<A: Into<Mailbox>>(mut self, address: A) -> EmailBuilder {
-        let mailbox = address.into();
-        self.cc.push(Address::Mailbox(mailbox));
-        self
-    }
-
-    /// Adds a `Bcc` header and stores the recipient address
-    pub fn bcc<A: Into<Mailbox>>(mut self, address: A) -> EmailBuilder {
-        let mailbox = address.into();
-        self.bcc.push(Address::Mailbox(mailbox));
-        self
-    }
-
-    /// Adds a `Reply-To` header
-    pub fn reply_to<A: Into<Mailbox>>(mut self, address: A) -> EmailBuilder {
-        let mailbox = address.into();
-        self.reply_to.push(Address::Mailbox(mailbox));
-        self
-    }
-
-    /// Adds a `In-Reply-To` header
-    pub fn in_reply_to(mut self, message_id: MessageId) -> EmailBuilder {
-        self.in_reply_to.push(message_id);
-        self
-    }
-
-    /// Adds a `References` header
-    pub fn references(mut self, message_id: MessageId) -> EmailBuilder {
-        self.references.push(message_id);
-        self
-    }
-
-    /// Adds a `Sender` header
-    pub fn sender<A: Into<Mailbox>>(mut self, address: A) -> EmailBuilder {
-        let mailbox = address.into();
-        self.sender = Some(mailbox);
-        self
-    }
-
-    /// Adds a `Subject` header
-    pub fn subject<S: Into<String>>(mut self, subject: S) -> EmailBuilder {
-        self.message = self.message.header(("Subject".to_string(), subject.into()));
-        self
-    }
-
-    /// Adds a `Date` header with the given date
-    pub fn date(mut self, date: &Tm) -> EmailBuilder {
-        self.message = self.message.header(("Date", Tm::rfc822z(date).to_string()));
-        self.date_issued = true;
-        self
-    }
-
-    /// Adds an attachment to the email from a file
-    ///
-    /// If not specified, the filename will be extracted from the file path.
-    pub fn attachment_from_file(
-        self,
-        path: &Path,
-        filename: Option<&str>,
-        content_type: &Mime,
-    ) -> Result<EmailBuilder, Error> {
-        self.attachment(
-            fs::read(path)?.as_slice(),
-            filename.unwrap_or(
-                path.file_name()
-                    .and_then(|x| x.to_str())
-                    .ok_or(EmailError::CannotParseFilename)?,
-            ),
-            content_type,
-        )
-    }
-
-    /// Adds an attachment to the email from a vector of bytes.
-    pub fn attachment(
-        self,
-        body: &[u8],
-        filename: &str,
-        content_type: &Mime,
-    ) -> Result<EmailBuilder, Error> {
-        let encoded_body = base64::encode(&body);
-        let content = PartBuilder::new()
-            .body(encoded_body)
-            .header((
-                "Content-Disposition",
-                format!("attachment; filename=\"{}\"", filename),
-            ))
-            .header(("Content-Type", content_type.to_string()))
-            .header(("Content-Transfer-Encoding", "base64"))
-            .build();
-
-        Ok(self.message_type(MimeMultipartType::Mixed).child(content))
-    }
-
-    /// Set the message type
-    pub fn message_type(mut self, message_type: MimeMultipartType) -> EmailBuilder {
-        self.message = self.message.message_type(message_type);
-        self
-    }
-
-    /// Adds a child
-    pub fn child(mut self, child: MimeMessage) -> EmailBuilder {
-        self.message = self.message.child(child);
-        self
-    }
-
-    /// Sets the email body to plain text content
-    pub fn text<S: Into<String>>(self, body: S) -> EmailBuilder {
-        let text = PartBuilder::new()
-            .body(body)
-            .header((
-                "Content-Type",
-                format!("{}", mime::TEXT_PLAIN_UTF_8).as_ref(),
-            ))
-            .build();
-        self.child(text)
-    }
-
-    /// Sets the email body to HTML content
-    pub fn html<S: Into<String>>(self, body: S) -> EmailBuilder {
-        let html = PartBuilder::new()
-            .body(body)
-            .header((
-                "Content-Type",
-                format!("{}", mime::TEXT_HTML_UTF_8).as_ref(),
-            ))
-            .build();
-        self.child(html)
-    }
-
-    /// Sets the email content
-    pub fn alternative<S: Into<String>, T: Into<String>>(
-        self,
-        body_html: S,
-        body_text: T,
-    ) -> EmailBuilder {
-        let text = PartBuilder::new()
-            .body(body_text)
-            .header((
-                "Content-Type",
-                format!("{}", mime::TEXT_PLAIN_UTF_8).as_ref(),
-            ))
-            .build();
-
-        let html = PartBuilder::new()
-            .body(body_html)
-            .header((
-                "Content-Type",
-                format!("{}", mime::TEXT_HTML_UTF_8).as_ref(),
-            ))
-            .build();
-
-        let alternate = PartBuilder::new()
-            .message_type(MimeMultipartType::Alternative)
-            .child(text)
-            .child(html);
-
-        self.message_type(MimeMultipartType::Mixed)
-            .child(alternate.build())
-    }
-
-    /// Sets the envelope for manual destination control
-    /// If this function is not called, the envelope will be calculated
-    /// from the "to" and "cc" addresses you set.
-    pub fn envelope(mut self, envelope: Envelope) -> EmailBuilder {
-        self.envelope = Some(envelope);
-        self
-    }
-
-    /// Builds the Email
-    pub fn build(mut self) -> Result<Email, Error> {
-        // If there are multiple addresses in "From", the "Sender" is required.
-        if self.from.len() >= 2 && self.sender.is_none() {
-            // So, we must find something to put as Sender.
-            for possible_sender in &self.from {
-                // Only a mailbox can be used as sender, not Address::Group.
-                if let Address::Mailbox(ref mbx) = *possible_sender {
-                    self.sender = Some(mbx.clone());
-                    break;
-                }
-            }
-            // Address::Group is not yet supported, so the line below will never panic.
-            // If groups are supported one day, add another Error for this case
-            //  and return it here, if sender_header is still None at this point.
-            assert!(self.sender.is_some());
-        }
-        // Add the sender header, if any.
-        if let Some(ref v) = self.sender {
-            self.message = self.message.header(("Sender", v.to_string().as_ref()));
-        }
-        // Calculate the envelope
-        let envelope = match self.envelope {
-            Some(e) => e,
-            None => {
-                // we need to generate the envelope
-                let mut to = vec![];
-                // add all receivers in to_header and cc_header
-                for receiver in self.to.iter().chain(self.cc.iter()).chain(self.bcc.iter()) {
-                    match *receiver {
-                        Address::Mailbox(ref m) => to.push(EmailAddress::from_str(&m.address)?),
-                        Address::Group(_, ref ms) => {
-                            for m in ms.iter() {
-                                to.push(EmailAddress::from_str(&m.address.clone())?);
-                            }
-                        }
-                    }
-                }
-                let from = Some(EmailAddress::from_str(&match self.sender {
-                    Some(x) => Ok(x.address.clone()), // if we have a sender_header, use it
-                    None => {
-                        // use a from header
-                        debug_assert!(self.from.len() <= 1); // else we'd have sender_header
-                        match self.from.first() {
-                            Some(a) => match *a {
-                                // if we have a from header
-                                Address::Mailbox(ref mailbox) => Ok(mailbox.address.clone()), // use it
-                                Address::Group(_, ref mailbox_list) => match mailbox_list.first() {
-                                    // if it's an author group, use the first author
-                                    Some(mailbox) => Ok(mailbox.address.clone()),
-                                    // for an empty author group (the rarest of the rare cases)
-                                    None => Err(EmailError::Envelope {
-                                        error: LettreError::MissingFrom,
-                                    }), // empty envelope sender
-                                },
-                            },
-                            // if we don't have a from header
-                            None => Err(EmailError::Envelope {
-                                error: LettreError::MissingFrom,
-                            }), // empty envelope sender
-                        }
-                    }
-                }?)?);
-                Envelope::new(from, to)?
-            }
-        };
-        // Add the collected addresses as mailbox-list all at once.
-        // The unwraps are fine because the conversions for Vec<Address> never errs.
-        if !self.to.is_empty() {
-            self.message = self
-                .message
-                .header(Header::new_with_value("To".into(), self.to).unwrap());
-        }
-        if !self.from.is_empty() {
-            self.message = self
-                .message
-                .header(Header::new_with_value("From".into(), self.from).unwrap());
-        } else if let Some(from) = envelope.from() {
-            let from = vec![Address::new_mailbox(from.to_string())];
-            self.message = self
-                .message
-                .header(Header::new_with_value("From".into(), from).unwrap());
-        } else {
-            Err(EmailError::Envelope {
-                error: LettreError::MissingFrom,
-            })?;
-        }
-        if !self.cc.is_empty() {
-            self.message = self
-                .message
-                .header(Header::new_with_value("Cc".into(), self.cc).unwrap());
-        }
-        if !self.reply_to.is_empty() {
-            self.message = self
-                .message
-                .header(Header::new_with_value("Reply-To".into(), self.reply_to).unwrap());
-        }
-        if !self.in_reply_to.is_empty() {
-            self.message = self.message.header(
-                Header::new_with_value("In-Reply-To".into(), self.in_reply_to.join(" ")).unwrap(),
-            );
-        }
-        if !self.references.is_empty() {
-            self.message = self.message.header(
-                Header::new_with_value("References".into(), self.references.join(" ")).unwrap(),
-            );
-        }
-
-        if !self.date_issued {
-            self.message = self
-                .message
-                .header(("Date", Tm::rfc822z(&now()).to_string().as_ref()));
-        }
-
-        self.message = self.message.header(("MIME-Version", "1.0"));
-
-        let message_id = Uuid::new_v4();
-
-        if let Ok(header) = Header::new_with_value(
-            "Message-ID".to_string(),
-            format!("<{}.lettre@localhost>", message_id),
-        ) {
-            self.message = self.message.header(header)
-        }
-
-        Ok(Email {
-            message: self.message.build().as_string().into_bytes(),
-            envelope,
-            message_id,
-        })
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::{EmailBuilder, SendableEmail};
-    use lettre::EmailAddress;
-    use time::now;
-
-    #[test]
-    fn test_multiple_from() {
-        let email_builder = EmailBuilder::new();
-        let date_now = now();
-        let email: SendableEmail = email_builder
-            .to("anna@example.com")
-            .from("dieter@example.com")
-            .from("joachim@example.com")
-            .date(&date_now)
-            .subject("Invitation")
-            .body("We invite you!")
-            .build()
-            .unwrap()
-            .into();
-        let id = email.message_id().to_string();
-        assert_eq!(
-            email.message_to_string().unwrap(),
-            format!(
-                "Date: {}\r\nSubject: Invitation\r\nSender: \
-                 <dieter@example.com>\r\nTo: <anna@example.com>\r\nFrom: \
-                 <dieter@example.com>, <joachim@example.com>\r\nMIME-Version: \
-                 1.0\r\nMessage-ID: <{}.lettre@localhost>\r\n\r\nWe invite you!\r\n",
-                date_now.rfc822z(),
-                id
-            )
-        );
-    }
-
-    #[test]
-    fn test_email_builder() {
-        let email_builder = EmailBuilder::new();
-        let date_now = now();
-
-        let email: SendableEmail = email_builder
-            .to("user@localhost")
-            .from("user@localhost")
-            .cc(("cc@localhost", "Alias"))
-            .bcc("bcc@localhost")
-            .reply_to("reply@localhost")
-            .in_reply_to("original".to_string())
-            .sender("sender@localhost")
-            .body("Hello World!")
-            .date(&date_now)
-            .subject("Hello")
-            .header(("X-test", "value"))
-            .build()
-            .unwrap()
-            .into();
-        let id = email.message_id().to_string();
-        assert_eq!(
-            email.message_to_string().unwrap(),
-            format!(
-                "Date: {}\r\nSubject: Hello\r\nX-test: value\r\nSender: \
-                 <sender@localhost>\r\nTo: <user@localhost>\r\nFrom: \
-                 <user@localhost>\r\nCc: \"Alias\" <cc@localhost>\r\n\
-                 Reply-To: <reply@localhost>\r\nIn-Reply-To: original\r\n\
-                 MIME-Version: 1.0\r\nMessage-ID: \
-                 <{}.lettre@localhost>\r\n\r\nHello World!\r\n",
-                date_now.rfc822z(),
-                id
-            )
-        );
-    }
-
-    #[test]
-    fn test_email_sendable() {
-        let email_builder = EmailBuilder::new();
-        let date_now = now();
-
-        let email: SendableEmail = email_builder
-            .to("user@localhost")
-            .from("user@localhost")
-            .cc(("cc@localhost", "Alias"))
-            .bcc("bcc@localhost")
-            .reply_to("reply@localhost")
-            .sender("sender@localhost")
-            .body("Hello World!")
-            .date(&date_now)
-            .subject("Hello")
-            .header(("X-test", "value"))
-            .build()
-            .unwrap()
-            .into();
-
-        assert_eq!(
-            email.envelope().from().unwrap().to_string(),
-            "sender@localhost".to_string()
-        );
-        assert_eq!(
-            email.envelope().to(),
-            vec![
-                EmailAddress::new("user@localhost".to_string()).unwrap(),
-                EmailAddress::new("cc@localhost".to_string()).unwrap(),
-                EmailAddress::new("bcc@localhost".to_string()).unwrap(),
-            ]
-            .as_slice()
-        );
-    }
-
-}

lettre_email/tests/build_with_envelope.rs

@@ -1,34 +0,0 @@
-extern crate lettre;
-extern crate lettre_email;
-use lettre::{EmailAddress, Envelope};
-use lettre_email::EmailBuilder;
-
-#[test]
-fn build_with_envelope_test() {
-    let e = Envelope::new(
-        Some(EmailAddress::new("from@example.org".to_string()).unwrap()),
-        vec![EmailAddress::new("to@example.org".to_string()).unwrap()],
-    )
-    .unwrap();
-    let _email = EmailBuilder::new()
-        .envelope(e)
-        .subject("subject")
-        .text("message")
-        .build()
-        .unwrap();
-}
-
-#[test]
-fn build_with_envelope_without_from_test() {
-    let e = Envelope::new(
-        None,
-        vec![EmailAddress::new("to@example.org".to_string()).unwrap()],
-    )
-    .unwrap();
-    let _email = EmailBuilder::new()
-        .envelope(e)
-        .subject("subject")
-        .text("message")
-        .build()
-        .unwrap_err();
-}

lettre_email/tests/skeptic.rs

@@ -1,49 +0,0 @@
-extern crate glob;
-
-use self::glob::glob;
-use std::env;
-use std::env::consts::EXE_EXTENSION;
-use std::path::Path;
-use std::process::Command;
-
-#[test]
-fn book_test() {
-    let mut book_path = env::current_dir().unwrap();
-    book_path.push(
-        Path::new(file!())
-            .parent()
-            .unwrap()
-            .parent()
-            .unwrap()
-            .parent()
-            .unwrap()
-            .join("../website/content/creating-messages"),
-    ); // For some reasons, calling .parent() once more gives us None...
-
-    for md in glob(&format!("{}/*.md", book_path.to_str().unwrap())).unwrap() {
-        skeptic_test(&md.unwrap());
-    }
-}
-
-fn skeptic_test(path: &Path) {
-    let rustdoc = Path::new("rustdoc").with_extension(EXE_EXTENSION);
-    let exe = env::current_exe().unwrap();
-    let depdir = exe.parent().unwrap();
-
-    let mut cmd = Command::new(rustdoc);
-    cmd.args(&["--verbose", "--test"])
-        .arg("-L")
-        .arg(&depdir)
-        .arg(path);
-
-    let result = cmd
-        .spawn()
-        .expect("Failed to spawn process")
-        .wait()
-        .expect("Failed to run process");
-
-    assert!(
-        result.success(),
-        format!("Failed to run rustdoc tests on {:?}!", path)
-    );
-}

src/address/envelope.rs

@@ -0,0 +1,154 @@
+#[cfg(feature = "builder")]
+use std::convert::TryFrom;
+
+use super::Address;
+#[cfg(feature = "builder")]
+use crate::message::header::{self, Headers};
+#[cfg(feature = "builder")]
+use crate::message::{Mailbox, Mailboxes};
+use crate::Error;
+
+/// Simple email envelope representation
+///
+/// We only accept mailboxes, and do not support source routes (as per RFC).
+#[derive(PartialEq, Eq, Clone, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Envelope {
+    /// The envelope recipient's addresses
+    ///
+    /// This can not be empty.
+    forward_path: Vec<Address>,
+    /// The envelope sender address
+    reverse_path: Option<Address>,
+}
+
+impl Envelope {
+    /// Creates a new envelope, which may fail if `to` is empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::str::FromStr;
+    /// # use lettre::Address;
+    /// # use lettre::address::Envelope;
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let sender = Address::from_str("from@email.com")?;
+    /// let recipients = vec![Address::from_str("to@email.com")?];
+    ///
+    /// let envelope = Envelope::new(Some(sender), recipients);
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// # Errors
+    ///
+    /// If `to` has no elements in it.
+    pub fn new(from: Option<Address>, to: Vec<Address>) -> Result<Envelope, Error> {
+        if to.is_empty() {
+            return Err(Error::MissingTo);
+        }
+        Ok(Envelope {
+            forward_path: to,
+            reverse_path: from,
+        })
+    }
+
+    /// Gets the destination addresses of the envelope.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::str::FromStr;
+    /// # use lettre::Address;
+    /// # use lettre::address::Envelope;
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let sender = Address::from_str("from@email.com")?;
+    /// let recipients = vec![Address::from_str("to@email.com")?];
+    ///
+    /// let envelope = Envelope::new(Some(sender), recipients.clone())?;
+    /// assert_eq!(envelope.to(), recipients.as_slice());
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn to(&self) -> &[Address] {
+        self.forward_path.as_slice()
+    }
+
+    /// Gets the sender of the envelope.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::str::FromStr;
+    /// # use lettre::Address;
+    /// # use lettre::address::Envelope;
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let sender = Address::from_str("from@email.com")?;
+    /// let recipients = vec![Address::from_str("to@email.com")?];
+    ///
+    /// let envelope = Envelope::new(Some(sender), recipients.clone())?;
+    /// assert!(envelope.from().is_some());
+    ///
+    /// let senderless = Envelope::new(None, recipients.clone())?;
+    /// assert!(senderless.from().is_none());
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn from(&self) -> Option<&Address> {
+        self.reverse_path.as_ref()
+    }
+
+    /// Check if any of the addresses in the envelope contains non-ascii chars
+    pub(crate) fn has_non_ascii_addresses(&self) -> bool {
+        self.reverse_path
+            .iter()
+            .chain(self.forward_path.iter())
+            .any(|a| !a.is_ascii())
+    }
+}
+
+#[cfg(feature = "builder")]
+impl TryFrom<&Headers> for Envelope {
+    type Error = Error;
+
+    fn try_from(headers: &Headers) -> Result<Self, Self::Error> {
+        let from = match headers.get::<header::Sender>() {
+            // If there is a Sender, use it
+            Some(header::Sender(a)) => Some(a.email.clone()),
+            // ... else try From
+            None => match headers.get::<header::From>() {
+                Some(header::From(a)) => {
+                    let from: Vec<Mailbox> = a.clone().into();
+                    if from.len() > 1 {
+                        return Err(Error::TooManyFrom);
+                    }
+                    Some(from[0].email.clone())
+                }
+                None => None,
+            },
+        };
+
+        fn add_addresses_from_mailboxes(
+            addresses: &mut Vec<Address>,
+            mailboxes: Option<&Mailboxes>,
+        ) {
+            if let Some(mailboxes) = mailboxes {
+                for mailbox in mailboxes.iter() {
+                    addresses.push(mailbox.email.clone());
+                }
+            }
+        }
+        let mut to = vec![];
+        add_addresses_from_mailboxes(&mut to, headers.get::<header::To>().map(|h| &h.0));
+        add_addresses_from_mailboxes(&mut to, headers.get::<header::Cc>().map(|h| &h.0));
+        add_addresses_from_mailboxes(&mut to, headers.get::<header::Bcc>().map(|h| &h.0));
+
+        Self::new(from, to)
+    }
+}

src/address/mod.rs

@@ -0,0 +1,12 @@
+//! Email addresses
+
+#[cfg(feature = "serde")]
+mod serde;
+
+mod envelope;
+mod types;
+
+pub use self::{
+    envelope::Envelope,
+    types::{Address, AddressError},
+};

src/address/serde.rs

@@ -0,0 +1,112 @@
+use std::fmt::{Formatter, Result as FmtResult};
+
+use serde::{
+    de::{Deserializer, Error as DeError, MapAccess, Visitor},
+    ser::Serializer,
+    Deserialize, Serialize,
+};
+
+use super::Address;
+
+impl Serialize for Address {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(self.as_ref())
+    }
+}
+
+impl<'de> Deserialize<'de> for Address {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        enum Field {
+            User,
+            Domain,
+        }
+
+        const FIELDS: &[&str] = &["user", "domain"];
+
+        impl<'de> Deserialize<'de> for Field {
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+            where
+                D: Deserializer<'de>,
+            {
+                struct FieldVisitor;
+
+                impl<'de> Visitor<'de> for FieldVisitor {
+                    type Value = Field;
+
+                    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+                        formatter.write_str("'user' or 'domain'")
+                    }
+
+                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
+                    where
+                        E: DeError,
+                    {
+                        match value {
+                            "user" => Ok(Field::User),
+                            "domain" => Ok(Field::Domain),
+                            _ => Err(DeError::unknown_field(value, FIELDS)),
+                        }
+                    }
+                }
+
+                deserializer.deserialize_identifier(FieldVisitor)
+            }
+        }
+
+        struct AddressVisitor;
+
+        impl<'de> Visitor<'de> for AddressVisitor {
+            type Value = Address;
+
+            fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+                formatter.write_str("email address string or object")
+            }
+
+            fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
+            where
+                E: DeError,
+            {
+                s.parse().map_err(DeError::custom)
+            }
+
+            fn visit_map<V>(self, mut map: V) -> Result<Self::Value, V::Error>
+            where
+                V: MapAccess<'de>,
+            {
+                let mut user = None;
+                let mut domain = None;
+                while let Some(key) = map.next_key()? {
+                    match key {
+                        Field::User => {
+                            if user.is_some() {
+                                return Err(DeError::duplicate_field("user"));
+                            }
+                            let val = map.next_value()?;
+                            Address::check_user(val).map_err(DeError::custom)?;
+                            user = Some(val);
+                        }
+                        Field::Domain => {
+                            if domain.is_some() {
+                                return Err(DeError::duplicate_field("domain"));
+                            }
+                            let val = map.next_value()?;
+                            Address::check_domain(val).map_err(DeError::custom)?;
+                            domain = Some(val);
+                        }
+                    }
+                }
+                let user: &str = user.ok_or_else(|| DeError::missing_field("user"))?;
+                let domain: &str = domain.ok_or_else(|| DeError::missing_field("domain"))?;
+                Ok(Address::new(user, domain).unwrap())
+            }
+        }
+
+        deserializer.deserialize_any(AddressVisitor)
+    }
+}

src/address/types.rs

@@ -0,0 +1,257 @@
+//! Representation of an email address
+
+use idna::domain_to_ascii;
+use once_cell::sync::Lazy;
+use regex::Regex;
+use std::{
+    convert::{TryFrom, TryInto},
+    error::Error,
+    ffi::OsStr,
+    fmt::{Display, Formatter, Result as FmtResult},
+    net::IpAddr,
+    str::FromStr,
+};
+
+/// Represents an email address with a user and a domain name.
+///
+/// This type contains email in canonical form (_user@domain.tld_).
+///
+/// **NOTE**: Enable feature "serde" to be able serialize/deserialize it using [serde](https://serde.rs/).
+///
+/// # Examples
+///
+/// You can create an `Address` from a user and a domain:
+///
+/// ```
+/// # use lettre::Address;
+/// # use std::error::Error;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let address = Address::new("example", "email.com")?;
+/// # Ok(())
+/// # }
+/// ```
+///
+/// You can also create an `Address` from a string literal by parsing it:
+///
+/// ```
+/// use std::str::FromStr;
+/// # use lettre::Address;
+/// # use std::error::Error;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let address = Address::from_str("example@email.com")?;
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Debug, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
+pub struct Address {
+    /// Complete address
+    serialized: String,
+    /// Index into `serialized` before the '@'
+    at_start: usize,
+}
+
+impl<U, D> TryFrom<(U, D)> for Address
+where
+    U: AsRef<str>,
+    D: AsRef<str>,
+{
+    type Error = AddressError;
+
+    fn try_from((user, domain): (U, D)) -> Result<Self, Self::Error> {
+        let user = user.as_ref();
+        Address::check_user(user)?;
+
+        let domain = domain.as_ref();
+        Address::check_domain(domain)?;
+
+        let serialized = format!("{}@{}", user, domain);
+        Ok(Address {
+            serialized,
+            at_start: user.len(),
+        })
+    }
+}
+
+// Regex from the specs
+// https://html.spec.whatwg.org/multipage/forms.html#valid-e-mail-address
+// It will mark esoteric email addresses like quoted string as invalid
+static USER_RE: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r"^(?i)[a-z0-9.!#$%&'*+/=?^_`{|}~-]+\z").unwrap());
+static DOMAIN_RE: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(
+        r"(?i)^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?:.[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?)*$",
+    )
+    .unwrap()
+});
+// literal form, ipv4 or ipv6 address (SMTP 4.1.3)
+static LITERAL_RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?i)\[([A-f0-9:\.]+)\]\z").unwrap());
+
+impl Address {
+    /// Creates a new email address from a user and domain.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::Address;
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let address = Address::new("example", "email.com")?;
+    /// let expected: Address = "example@email.com".parse()?;
+    /// assert_eq!(expected, address);
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn new<U: AsRef<str>, D: AsRef<str>>(user: U, domain: D) -> Result<Self, AddressError> {
+        (user, domain).try_into()
+    }
+
+    /// Gets the user portion of the `Address`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::Address;
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let address = Address::new("example", "email.com")?;
+    /// assert_eq!("example", address.user());
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn user(&self) -> &str {
+        &self.serialized[..self.at_start]
+    }
+
+    /// Gets the domain portion of the `Address`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::Address;
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let address = Address::new("example", "email.com")?;
+    /// assert_eq!("email.com", address.domain());
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn domain(&self) -> &str {
+        &self.serialized[self.at_start + 1..]
+    }
+
+    pub(super) fn check_user(user: &str) -> Result<(), AddressError> {
+        if USER_RE.is_match(user) {
+            Ok(())
+        } else {
+            Err(AddressError::InvalidUser)
+        }
+    }
+
+    pub(super) fn check_domain(domain: &str) -> Result<(), AddressError> {
+        Address::check_domain_ascii(domain).or_else(|_| {
+            domain_to_ascii(domain)
+                .map_err(|_| AddressError::InvalidDomain)
+                .and_then(|domain| Address::check_domain_ascii(&domain))
+        })
+    }
+
+    fn check_domain_ascii(domain: &str) -> Result<(), AddressError> {
+        if DOMAIN_RE.is_match(domain) {
+            return Ok(());
+        }
+
+        if let Some(caps) = LITERAL_RE.captures(domain) {
+            if let Some(cap) = caps.get(1) {
+                if cap.as_str().parse::<IpAddr>().is_ok() {
+                    return Ok(());
+                }
+            }
+        }
+
+        Err(AddressError::InvalidDomain)
+    }
+
+    /// Check if the address contains non-ascii chars
+    pub(super) fn is_ascii(&self) -> bool {
+        self.serialized.is_ascii()
+    }
+}
+
+impl Display for Address {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        f.write_str(&self.serialized)
+    }
+}
+
+impl FromStr for Address {
+    type Err = AddressError;
+
+    fn from_str(val: &str) -> Result<Self, AddressError> {
+        let mut parts = val.rsplitn(2, '@');
+        let domain = parts.next().ok_or(AddressError::MissingParts)?;
+        let user = parts.next().ok_or(AddressError::MissingParts)?;
+
+        Address::check_user(user)?;
+        Address::check_domain(domain)?;
+        Ok(Address {
+            serialized: val.into(),
+            at_start: user.len(),
+        })
+    }
+}
+
+impl AsRef<str> for Address {
+    fn as_ref(&self) -> &str {
+        &self.serialized
+    }
+}
+
+impl AsRef<OsStr> for Address {
+    fn as_ref(&self) -> &OsStr {
+        self.serialized.as_ref()
+    }
+}
+
+#[derive(Debug, PartialEq, Clone, Copy)]
+/// Errors in email addresses parsing
+pub enum AddressError {
+    MissingParts,
+    Unbalanced,
+    InvalidUser,
+    InvalidDomain,
+    InvalidUtf8b,
+}
+
+impl Error for AddressError {}
+
+impl Display for AddressError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        match self {
+            AddressError::MissingParts => f.write_str("Missing domain or user"),
+            AddressError::Unbalanced => f.write_str("Unbalanced angle bracket"),
+            AddressError::InvalidUser => f.write_str("Invalid email user"),
+            AddressError::InvalidDomain => f.write_str("Invalid email domain"),
+            AddressError::InvalidUtf8b => f.write_str("Invalid UTF8b data"),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_address() {
+        let addr_str = "something@example.com";
+        let addr = Address::from_str(addr_str).unwrap();
+        let addr2 = Address::new("something", "example.com").unwrap();
+        assert_eq!(addr, addr2);
+        assert_eq!(addr.user(), "something");
+        assert_eq!(addr.domain(), "example.com");
+        assert_eq!(addr2.user(), "something");
+        assert_eq!(addr2.domain(), "example.com");
+    }
+}

src/error.rs

@@ -0,0 +1,54 @@
+//! Error type for email messages
+
+use std::{
+    error::Error as StdError,
+    fmt::{self, Display, Formatter},
+};
+
+// FIXME message-specific errors
+/// Error type for email content
+#[derive(Debug)]
+pub enum Error {
+    /// Missing from in envelope
+    MissingFrom,
+    /// Missing to in envelope
+    MissingTo,
+    /// Can only be one from in envelope
+    TooManyFrom,
+    /// Invalid email: missing at
+    EmailMissingAt,
+    /// Invalid email: missing local part
+    EmailMissingLocalPart,
+    /// Invalid email: missing domain
+    EmailMissingDomain,
+    /// Cannot parse filename for attachment
+    CannotParseFilename,
+    /// IO error
+    Io(std::io::Error),
+    /// Non-ASCII chars
+    NonAsciiChars,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), fmt::Error> {
+        match self {
+            Error::MissingFrom => f.write_str("missing source address, invalid envelope"),
+            Error::MissingTo => f.write_str("missing destination address, invalid envelope"),
+            Error::TooManyFrom => f.write_str("there can only be one source address"),
+            Error::EmailMissingAt => f.write_str("missing @ in email address"),
+            Error::EmailMissingLocalPart => f.write_str("missing local part in email address"),
+            Error::EmailMissingDomain => f.write_str("missing domain in email address"),
+            Error::CannotParseFilename => f.write_str("could not parse attachment filename"),
+            Error::NonAsciiChars => f.write_str("contains non-ASCII chars"),
+            Error::Io(e) => e.fmt(f),
+        }
+    }
+}
+
+impl From<std::io::Error> for Error {
+    fn from(err: std::io::Error) -> Error {
+        Error::Io(err)
+    }
+}
+
+impl StdError for Error {}

src/executor.rs

@@ -0,0 +1,232 @@
+use async_trait::async_trait;
+
+#[cfg(feature = "file-transport")]
+use std::io::Result as IoResult;
+#[cfg(feature = "file-transport")]
+use std::path::Path;
+
+#[cfg(all(
+    feature = "smtp-transport",
+    any(feature = "tokio02", feature = "tokio1", feature = "async-std1")
+))]
+use crate::transport::smtp::client::AsyncSmtpConnection;
+#[cfg(all(
+    feature = "smtp-transport",
+    any(feature = "tokio02", feature = "tokio1", feature = "async-std1")
+))]
+use crate::transport::smtp::client::Tls;
+#[cfg(all(
+    feature = "smtp-transport",
+    any(feature = "tokio02", feature = "tokio1", feature = "async-std1")
+))]
+use crate::transport::smtp::extension::ClientId;
+#[cfg(all(
+    feature = "smtp-transport",
+    any(feature = "tokio02", feature = "tokio1", feature = "async-std1")
+))]
+use crate::transport::smtp::Error;
+
+#[async_trait]
+pub trait Executor: Send + Sync + private::Sealed {
+    #[doc(hidden)]
+    #[cfg(feature = "smtp-transport")]
+    async fn connect(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls: &Tls,
+    ) -> Result<AsyncSmtpConnection, Error>;
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport-envelope")]
+    async fn fs_read(path: &Path) -> IoResult<Vec<u8>>;
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport")]
+    async fn fs_write(path: &Path, contents: &[u8]) -> IoResult<()>;
+}
+
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+#[cfg(feature = "tokio02")]
+#[cfg_attr(docsrs, doc(cfg(feature = "tokio02")))]
+pub struct Tokio02Executor;
+
+#[async_trait]
+#[cfg(feature = "tokio02")]
+impl Executor for Tokio02Executor {
+    #[doc(hidden)]
+    #[cfg(feature = "smtp-transport")]
+    async fn connect(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls: &Tls,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        #[allow(clippy::match_single_binding)]
+        let tls_parameters = match tls {
+            #[cfg(any(feature = "tokio02-native-tls", feature = "tokio02-rustls-tls"))]
+            Tls::Wrapper(ref tls_parameters) => Some(tls_parameters.clone()),
+            _ => None,
+        };
+        #[allow(unused_mut)]
+        let mut conn =
+            AsyncSmtpConnection::connect_tokio02(hostname, port, hello_name, tls_parameters)
+                .await?;
+
+        #[cfg(any(feature = "tokio02-native-tls", feature = "tokio02-rustls-tls"))]
+        match tls {
+            Tls::Opportunistic(ref tls_parameters) => {
+                if conn.can_starttls() {
+                    conn.starttls(tls_parameters.clone(), hello_name).await?;
+                }
+            }
+            Tls::Required(ref tls_parameters) => {
+                conn.starttls(tls_parameters.clone(), hello_name).await?;
+            }
+            _ => (),
+        }
+
+        Ok(conn)
+    }
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport-envelope")]
+    async fn fs_read(path: &Path) -> IoResult<Vec<u8>> {
+        tokio02_crate::fs::read(path).await
+    }
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport")]
+    async fn fs_write(path: &Path, contents: &[u8]) -> IoResult<()> {
+        tokio02_crate::fs::write(path, contents).await
+    }
+}
+
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+#[cfg(feature = "tokio1")]
+#[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
+pub struct Tokio1Executor;
+
+#[async_trait]
+#[cfg(feature = "tokio1")]
+impl Executor for Tokio1Executor {
+    #[doc(hidden)]
+    #[cfg(feature = "smtp-transport")]
+    async fn connect(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls: &Tls,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        #[allow(clippy::match_single_binding)]
+        let tls_parameters = match tls {
+            #[cfg(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))]
+            Tls::Wrapper(ref tls_parameters) => Some(tls_parameters.clone()),
+            _ => None,
+        };
+        #[allow(unused_mut)]
+        let mut conn =
+            AsyncSmtpConnection::connect_tokio1(hostname, port, hello_name, tls_parameters).await?;
+
+        #[cfg(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))]
+        match tls {
+            Tls::Opportunistic(ref tls_parameters) => {
+                if conn.can_starttls() {
+                    conn.starttls(tls_parameters.clone(), hello_name).await?;
+                }
+            }
+            Tls::Required(ref tls_parameters) => {
+                conn.starttls(tls_parameters.clone(), hello_name).await?;
+            }
+            _ => (),
+        }
+
+        Ok(conn)
+    }
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport-envelope")]
+    async fn fs_read(path: &Path) -> IoResult<Vec<u8>> {
+        tokio1_crate::fs::read(path).await
+    }
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport")]
+    async fn fs_write(path: &Path, contents: &[u8]) -> IoResult<()> {
+        tokio1_crate::fs::write(path, contents).await
+    }
+}
+
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+#[cfg(feature = "async-std1")]
+#[cfg_attr(docsrs, doc(cfg(feature = "async-std1")))]
+pub struct AsyncStd1Executor;
+
+#[async_trait]
+#[cfg(feature = "async-std1")]
+impl Executor for AsyncStd1Executor {
+    #[doc(hidden)]
+    #[cfg(feature = "smtp-transport")]
+    async fn connect(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls: &Tls,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        #[allow(clippy::match_single_binding)]
+        let tls_parameters = match tls {
+            #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+            Tls::Wrapper(ref tls_parameters) => Some(tls_parameters.clone()),
+            _ => None,
+        };
+        #[allow(unused_mut)]
+        let mut conn =
+            AsyncSmtpConnection::connect_asyncstd1(hostname, port, hello_name, tls_parameters)
+                .await?;
+
+        #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+        match tls {
+            Tls::Opportunistic(ref tls_parameters) => {
+                if conn.can_starttls() {
+                    conn.starttls(tls_parameters.clone(), hello_name).await?;
+                }
+            }
+            Tls::Required(ref tls_parameters) => {
+                conn.starttls(tls_parameters.clone(), hello_name).await?;
+            }
+            _ => (),
+        }
+
+        Ok(conn)
+    }
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport-envelope")]
+    async fn fs_read(path: &Path) -> IoResult<Vec<u8>> {
+        async_std::fs::read(path).await
+    }
+
+    #[doc(hidden)]
+    #[cfg(feature = "file-transport")]
+    async fn fs_write(path: &Path, contents: &[u8]) -> IoResult<()> {
+        async_std::fs::write(path, contents).await
+    }
+}
+
+mod private {
+    use super::*;
+
+    pub trait Sealed {}
+
+    #[cfg(feature = "tokio02")]
+    impl Sealed for Tokio02Executor {}
+
+    #[cfg(feature = "tokio1")]
+    impl Sealed for Tokio1Executor {}
+
+    #[cfg(feature = "async-std1")]
+    impl Sealed for AsyncStd1Executor {}
+}

src/lib.rs

@@ -0,0 +1,157 @@
+//! Lettre is an email library that allows creating and sending messages. It provides:
+//!
+//! * An easy to use email builder
+//! * Pluggable email transports
+//! * Unicode support
+//! * Secure defaults
+//!
+//! Lettre requires Rust 1.45 or newer.
+//!
+//! ## Optional features
+//!
+//! * **builder**: Message builder
+//! * **file-transport**: Transport that write messages into a file
+//! * **file-transport-envelope**: Allow writing the envelope into a JSON file
+//! * **smtp-transport**: Transport over SMTP
+//! * **sendmail-transport**: Transport over SMTP
+//! * **rustls-tls**: TLS support with the `rustls` crate
+//! * **native-tls**: TLS support with the `native-tls` crate
+//! * **tokio02**: Allow to asyncronously send emails using tokio 0.2.x
+//! * **tokio02-rustls-tls**: Async TLS support with the `rustls` crate using tokio 0.2
+//! * **tokio02-native-tls**: Async TLS support with the `native-tls` crate using tokio 0.2
+//! * **tokio1**: Allow to asyncronously send emails using tokio 1.x
+//! * **tokio1-rustls-tls**: Async TLS support with the `rustls` crate using tokio 1.x
+//! * **tokio1-native-tls**: Async TLS support with the `native-tls` crate using tokio 1.x
+//! * **async-std1**: Allow to asynchronously send emails using async-std 1.x
+//! * NOTE: native-tls isn't supported with async-std at the moment
+//! * **async-std1-rustls-tls**: Async TLS support with the `rustls` crate using async-std 1.x
+//! * **r2d2**: Connection pool for SMTP transport
+//! * **tracing**: Logging using the `tracing` crate
+//! * **serde**: Serialization/Deserialization of entities
+//! * **hostname**: Ability to try to use actual hostname in SMTP transaction
+
+#![doc(html_root_url = "https://docs.rs/crate/lettre/0.10.0-beta.2")]
+#![doc(html_favicon_url = "https://lettre.rs/favicon.ico")]
+#![doc(html_logo_url = "https://avatars0.githubusercontent.com/u/15113230?v=4")]
+#![forbid(unsafe_code)]
+#![deny(
+    missing_copy_implementations,
+    trivial_casts,
+    trivial_numeric_casts,
+    unstable_features,
+    unused_import_braces,
+    rust_2018_idioms
+)]
+#![cfg_attr(docsrs, feature(doc_cfg))]
+
+pub mod address;
+pub mod error;
+#[cfg(all(any(feature = "tokio02", feature = "tokio1", feature = "async-std1")))]
+mod executor;
+#[cfg(feature = "builder")]
+#[cfg_attr(docsrs, doc(cfg(feature = "builder")))]
+pub mod message;
+pub mod transport;
+
+#[cfg(feature = "builder")]
+#[macro_use]
+extern crate hyperx;
+
+#[cfg(feature = "async-std1")]
+pub use self::executor::AsyncStd1Executor;
+#[cfg(all(any(feature = "tokio02", feature = "tokio1", feature = "async-std1")))]
+pub use self::executor::Executor;
+#[cfg(feature = "tokio02")]
+pub use self::executor::Tokio02Executor;
+#[cfg(feature = "tokio1")]
+pub use self::executor::Tokio1Executor;
+#[cfg(all(any(feature = "tokio02", feature = "tokio1", feature = "async-std1")))]
+pub use self::transport::AsyncTransport;
+pub use crate::address::Address;
+#[cfg(feature = "builder")]
+pub use crate::message::Message;
+#[cfg(all(
+    feature = "file-transport",
+    any(feature = "tokio02", feature = "tokio1", feature = "async-std1")
+))]
+pub use crate::transport::file::AsyncFileTransport;
+#[cfg(feature = "file-transport")]
+pub use crate::transport::file::FileTransport;
+#[cfg(all(
+    feature = "sendmail-transport",
+    any(feature = "tokio02", feature = "tokio1", feature = "async-std1")
+))]
+pub use crate::transport::sendmail::AsyncSendmailTransport;
+#[cfg(feature = "sendmail-transport")]
+pub use crate::transport::sendmail::SendmailTransport;
+#[cfg(all(
+    feature = "smtp-transport",
+    any(feature = "tokio02", feature = "tokio1")
+))]
+pub use crate::transport::smtp::AsyncSmtpTransport;
+pub use crate::transport::Transport;
+use crate::{address::Envelope, error::Error};
+
+#[cfg(feature = "smtp-transport")]
+pub use crate::transport::smtp::SmtpTransport;
+
+#[cfg(test)]
+#[cfg(feature = "builder")]
+mod test {
+    use super::*;
+    use crate::message::{header, Mailbox, Mailboxes};
+    use hyperx::header::Headers;
+    use std::convert::TryFrom;
+
+    #[test]
+    fn envelope_from_headers() {
+        let from = Mailboxes::new().with("kayo@example.com".parse().unwrap());
+        let to = Mailboxes::new().with("amousset@example.com".parse().unwrap());
+
+        let mut headers = Headers::new();
+        headers.set(header::From(from));
+        headers.set(header::To(to));
+
+        assert_eq!(
+            Envelope::try_from(&headers).unwrap(),
+            Envelope::new(
+                Some(Address::new("kayo", "example.com").unwrap()),
+                vec![Address::new("amousset", "example.com").unwrap()]
+            )
+            .unwrap()
+        );
+    }
+
+    #[test]
+    fn envelope_from_headers_sender() {
+        let from = Mailboxes::new().with("kayo@example.com".parse().unwrap());
+        let sender = Mailbox::new(None, "kayo2@example.com".parse().unwrap());
+        let to = Mailboxes::new().with("amousset@example.com".parse().unwrap());
+
+        let mut headers = Headers::new();
+        headers.set(header::From(from));
+        headers.set(header::Sender(sender));
+        headers.set(header::To(to));
+
+        assert_eq!(
+            Envelope::try_from(&headers).unwrap(),
+            Envelope::new(
+                Some(Address::new("kayo2", "example.com").unwrap()),
+                vec![Address::new("amousset", "example.com").unwrap()]
+            )
+            .unwrap()
+        );
+    }
+
+    #[test]
+    fn envelope_from_headers_no_to() {
+        let from = Mailboxes::new().with("kayo@example.com".parse().unwrap());
+        let sender = Mailbox::new(None, "kayo2@example.com".parse().unwrap());
+
+        let mut headers = Headers::new();
+        headers.set(header::From(from));
+        headers.set(header::Sender(sender));
+
+        assert!(Envelope::try_from(&headers).is_err(),);
+    }
+}

src/message/body.rs

@@ -0,0 +1,581 @@
+use std::{
+    io::{self, Write},
+    ops::Deref,
+};
+
+use crate::message::header::ContentTransferEncoding;
+
+/// A [`Message`][super::Message] or [`SinglePart`][super::SinglePart] body that has already been encoded.
+#[derive(Debug, Clone)]
+pub struct Body {
+    buf: Vec<u8>,
+    encoding: ContentTransferEncoding,
+}
+
+/// Either a `Vec<u8>` or a `String`.
+///
+/// If the content is valid utf-8 a `String` should be passed, as it
+/// makes for a more efficient `Content-Transfer-Encoding` to be chosen.
+#[derive(Debug, Clone)]
+pub enum MaybeString {
+    Binary(Vec<u8>),
+    String(String),
+}
+
+impl Body {
+    /// Encode the supplied `buf`, making it ready to be sent as a body.
+    ///
+    /// Takes a `Vec<u8>` or a `String`.
+    ///
+    /// Automatically chooses the most efficient encoding between
+    /// `7bit`, `quoted-printable` and `base64`.
+    ///
+    /// If `buf` is valid utf-8 a `String` should be supplied, as `String`s
+    /// can be encoded as `7bit` or `quoted-printable`, while `Vec<u8>` always
+    /// get encoded as `base64`.
+    pub fn new<B: Into<MaybeString>>(buf: B) -> Self {
+        let buf: MaybeString = buf.into();
+
+        let encoding = buf.encoding();
+        Self::new_impl(buf.into(), encoding)
+    }
+
+    /// Encode the supplied `buf`, using the provided `encoding`.
+    ///
+    /// [`Body::new`] is generally the better option.
+    ///
+    /// Returns an [`Err`] giving back the supplied `buf`, in case the chosen
+    /// encoding would have resulted into `buf` being encoded
+    /// into an invalid body.
+    pub fn new_with_encoding<B: Into<MaybeString>>(
+        buf: B,
+        encoding: ContentTransferEncoding,
+    ) -> Result<Self, Vec<u8>> {
+        let buf: MaybeString = buf.into();
+
+        if !buf.is_encoding_ok(encoding) {
+            return Err(buf.into());
+        }
+
+        Ok(Self::new_impl(buf.into(), encoding))
+    }
+
+    /// Builds a new `Body` using a pre-encoded buffer.
+    ///
+    /// **Generally not you want.**
+    ///
+    /// `buf` shouldn't contain non-ascii characters, lines longer than 1000 characters or nul bytes.
+    #[inline]
+    pub fn dangerous_pre_encoded(buf: Vec<u8>, encoding: ContentTransferEncoding) -> Self {
+        Self { buf, encoding }
+    }
+
+    /// Encodes the supplied `buf` using the provided `encoding`
+    fn new_impl(buf: Vec<u8>, encoding: ContentTransferEncoding) -> Self {
+        match encoding {
+            ContentTransferEncoding::SevenBit
+            | ContentTransferEncoding::EightBit
+            | ContentTransferEncoding::Binary => Self { buf, encoding },
+            ContentTransferEncoding::QuotedPrintable => {
+                let encoded = quoted_printable::encode(buf);
+
+                Self::dangerous_pre_encoded(encoded, ContentTransferEncoding::QuotedPrintable)
+            }
+            ContentTransferEncoding::Base64 => {
+                let base64_len = buf.len() * 4 / 3 + 4;
+                let base64_endings_len = base64_len + base64_len / LINE_MAX_LENGTH;
+
+                let mut out = Vec::with_capacity(base64_endings_len);
+                {
+                    let writer = LineWrappingWriter::new(&mut out, LINE_MAX_LENGTH);
+                    let mut writer = base64::write::EncoderWriter::new(writer, base64::STANDARD);
+
+                    // TODO: use writer.write_all(self.as_ref()).expect("base64 encoding never fails");
+
+                    // modified Write::write_all to work around base64 crate bug
+                    // TODO: remove once https://github.com/marshallpierce/rust-base64/issues/148 is fixed
+                    {
+                        let mut buf: &[u8] = buf.as_ref();
+                        while !buf.is_empty() {
+                            match writer.write(buf) {
+                                Ok(0) => {
+                                    // ignore 0 writes
+                                }
+                                Ok(n) => {
+                                    buf = &buf[n..];
+                                }
+                                Err(ref e) if e.kind() == std::io::ErrorKind::Interrupted => {}
+                                Err(e) => panic!("base64 encoding never fails: {}", e),
+                            }
+                        }
+                    }
+                }
+
+                Self::dangerous_pre_encoded(out, ContentTransferEncoding::Base64)
+            }
+        }
+    }
+
+    /// Returns the length of this `Body` in bytes.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.buf.len()
+    }
+
+    /// Returns `true` if this `Body` has a length of zero, `false` otherwise.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.buf.is_empty()
+    }
+
+    /// Returns the `Content-Transfer-Encoding` of this `Body`.
+    #[inline]
+    pub fn encoding(&self) -> ContentTransferEncoding {
+        self.encoding
+    }
+
+    /// Consumes `Body` and returns the inner `Vec<u8>`
+    #[inline]
+    pub fn into_vec(self) -> Vec<u8> {
+        self.buf
+    }
+}
+
+impl MaybeString {
+    /// Suggests the best `Content-Transfer-Encoding` to be used for this `MaybeString`
+    ///
+    /// If the `MaybeString` was created from a `String` composed only of US-ASCII
+    /// characters, with no lines longer than 1000 characters, then 7bit
+    /// encoding will be used, else quoted-printable will be chosen.
+    ///
+    /// If the `MaybeString` was instead created from a `Vec<u8>`, base64 encoding is always
+    /// chosen.
+    ///
+    /// `8bit` and `binary` encodings are never returned, as they may not be
+    /// supported by all SMTP servers.
+    pub fn encoding(&self) -> ContentTransferEncoding {
+        match &self {
+            Self::String(s) if is_7bit_encoded(s.as_ref()) => ContentTransferEncoding::SevenBit,
+            // TODO: consider when base64 would be a better option because of output size
+            Self::String(_) => ContentTransferEncoding::QuotedPrintable,
+            Self::Binary(_) => ContentTransferEncoding::Base64,
+        }
+    }
+
+    /// Returns `true` if using `encoding` to encode this `MaybeString`
+    /// would result into an invalid encoded body.
+    fn is_encoding_ok(&self, encoding: ContentTransferEncoding) -> bool {
+        match encoding {
+            ContentTransferEncoding::SevenBit => is_7bit_encoded(&self),
+            ContentTransferEncoding::EightBit => is_8bit_encoded(&self),
+            ContentTransferEncoding::Binary
+            | ContentTransferEncoding::QuotedPrintable
+            | ContentTransferEncoding::Base64 => true,
+        }
+    }
+}
+
+/// A trait for something that takes an encoded [`Body`].
+///
+/// Used by [`MessageBuilder::body`][super::MessageBuilder::body] and
+/// [`SinglePartBuilder::body`][super::SinglePartBuilder::body],
+/// which can either take something that can be encoded into [`Body`]
+/// or a pre-encoded [`Body`].
+///
+/// If `encoding` is `None` the best encoding between `7bit`, `quoted-printable`
+/// and `base64` is chosen based on the input body. **Best option.**
+///
+/// If `encoding` is `Some` the supplied encoding is used.
+/// **NOTE:** if using the specified `encoding` would result into a malformed
+/// body, this will panic!
+pub trait IntoBody {
+    fn into_body(self, encoding: Option<ContentTransferEncoding>) -> Body;
+}
+
+impl<T> IntoBody for T
+where
+    T: Into<MaybeString>,
+{
+    fn into_body(self, encoding: Option<ContentTransferEncoding>) -> Body {
+        match encoding {
+            Some(encoding) => Body::new_with_encoding(self, encoding).expect("invalid encoding"),
+            None => Body::new(self),
+        }
+    }
+}
+
+impl IntoBody for Body {
+    fn into_body(self, encoding: Option<ContentTransferEncoding>) -> Body {
+        let _ = encoding;
+
+        self
+    }
+}
+
+impl AsRef<[u8]> for Body {
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.buf.as_ref()
+    }
+}
+
+impl From<Vec<u8>> for MaybeString {
+    #[inline]
+    fn from(b: Vec<u8>) -> Self {
+        Self::Binary(b)
+    }
+}
+
+impl From<String> for MaybeString {
+    #[inline]
+    fn from(s: String) -> Self {
+        Self::String(s)
+    }
+}
+
+impl From<MaybeString> for Vec<u8> {
+    #[inline]
+    fn from(s: MaybeString) -> Self {
+        match s {
+            MaybeString::Binary(b) => b,
+            MaybeString::String(s) => s.into(),
+        }
+    }
+}
+
+impl Deref for MaybeString {
+    type Target = [u8];
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        match self {
+            Self::Binary(b) => b.as_ref(),
+            Self::String(s) => s.as_ref(),
+        }
+    }
+}
+
+/// Checks whether it contains only US-ASCII characters,
+/// and no lines are longer than 1000 characters including the `\n` character.
+///
+/// Most efficient content encoding available
+fn is_7bit_encoded(buf: &[u8]) -> bool {
+    buf.is_ascii() && !contains_too_long_lines(buf)
+}
+
+/// Checks that no lines are longer than 1000 characters,
+/// including the `\n` character.
+/// NOTE: 8bit isn't supported by all SMTP servers.
+fn is_8bit_encoded(buf: &[u8]) -> bool {
+    !contains_too_long_lines(buf)
+}
+
+/// Checks if there are lines that are longer than 1000 characters,
+/// including the `\n` character.
+fn contains_too_long_lines(buf: &[u8]) -> bool {
+    buf.len() > 1000 && buf.split(|&b| b == b'\n').any(|line| line.len() > 999)
+}
+
+const LINE_SEPARATOR: &[u8] = b"\r\n";
+const LINE_MAX_LENGTH: usize = 78 - LINE_SEPARATOR.len();
+
+/// A `Write`r that inserts a line separator `\r\n` every `max_line_length` bytes.
+struct LineWrappingWriter<'a, W> {
+    writer: &'a mut W,
+    current_line_length: usize,
+    max_line_length: usize,
+}
+
+impl<'a, W> LineWrappingWriter<'a, W> {
+    pub fn new(writer: &'a mut W, max_line_length: usize) -> Self {
+        Self {
+            writer,
+            current_line_length: 0,
+            max_line_length,
+        }
+    }
+}
+
+impl<'a, W> Write for LineWrappingWriter<'a, W>
+where
+    W: Write,
+{
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let remaining_line_len = self.max_line_length - self.current_line_length;
+        let write_len = std::cmp::min(buf.len(), remaining_line_len);
+
+        self.writer.write_all(&buf[..write_len])?;
+
+        if remaining_line_len == write_len {
+            self.writer.write_all(LINE_SEPARATOR)?;
+
+            self.current_line_length = 0;
+        } else {
+            self.current_line_length += write_len;
+        }
+
+        Ok(write_len)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.writer.flush()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::{Body, ContentTransferEncoding};
+
+    #[test]
+    fn seven_bit_detect() {
+        let encoded = Body::new(String::from("Hello, world!"));
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::SevenBit);
+        assert_eq!(encoded.as_ref(), b"Hello, world!");
+    }
+
+    #[test]
+    fn seven_bit_encode() {
+        let encoded = Body::new_with_encoding(
+            String::from("Hello, world!"),
+            ContentTransferEncoding::SevenBit,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::SevenBit);
+        assert_eq!(encoded.as_ref(), b"Hello, world!");
+    }
+
+    #[test]
+    fn seven_bit_too_long_detect() {
+        let encoded = Body::new("Hello, world!".repeat(100));
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::QuotedPrintable);
+        assert_eq!(
+            encoded.as_ref(),
+            concat!(
+                "Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, wor=\r\n",
+                "ld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, =\r\n",
+                "world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hell=\r\n",
+                "o, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!H=\r\n",
+                "ello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, worl=\r\n",
+                "d!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, w=\r\n",
+                "orld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello=\r\n",
+                ", world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!He=\r\n",
+                "llo, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world=\r\n",
+                "!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, wo=\r\n",
+                "rld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello,=\r\n",
+                " world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hel=\r\n",
+                "lo, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!=\r\n",
+                "Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, wor=\r\n",
+                "ld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, =\r\n",
+                "world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hell=\r\n",
+                "o, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!H=\r\n",
+                "ello, world!Hello, world!"
+            )
+            .as_bytes()
+        );
+    }
+
+    #[test]
+    fn seven_bit_too_long_fail() {
+        let result = Body::new_with_encoding(
+            "Hello, world!".repeat(100),
+            ContentTransferEncoding::SevenBit,
+        );
+
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn seven_bit_too_long_encode_quotedprintable() {
+        let encoded = Body::new_with_encoding(
+            "Hello, world!".repeat(100),
+            ContentTransferEncoding::QuotedPrintable,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::QuotedPrintable);
+        assert_eq!(
+            encoded.as_ref(),
+            concat!(
+                "Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, wor=\r\n",
+                "ld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, =\r\n",
+                "world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hell=\r\n",
+                "o, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!H=\r\n",
+                "ello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, worl=\r\n",
+                "d!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, w=\r\n",
+                "orld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello=\r\n",
+                ", world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!He=\r\n",
+                "llo, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world=\r\n",
+                "!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, wo=\r\n",
+                "rld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello,=\r\n",
+                " world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hel=\r\n",
+                "lo, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!=\r\n",
+                "Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, wor=\r\n",
+                "ld!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, =\r\n",
+                "world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hell=\r\n",
+                "o, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!H=\r\n",
+                "ello, world!Hello, world!"
+            )
+            .as_bytes()
+        );
+    }
+
+    #[test]
+    fn seven_bit_invalid() {
+        let result = Body::new_with_encoding(
+            String::from("Привет, мир!"),
+            ContentTransferEncoding::SevenBit,
+        );
+
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn eight_bit_encode() {
+        let encoded = Body::new_with_encoding(
+            String::from("Привет, мир!"),
+            ContentTransferEncoding::EightBit,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::EightBit);
+        assert_eq!(encoded.as_ref(), "Привет, мир!".as_bytes());
+    }
+
+    #[test]
+    fn eight_bit_too_long_fail() {
+        let result = Body::new_with_encoding(
+            "Привет, мир!".repeat(200),
+            ContentTransferEncoding::EightBit,
+        );
+
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn quoted_printable_detect() {
+        let encoded = Body::new(String::from("Привет, мир!"));
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::QuotedPrintable);
+        assert_eq!(
+            encoded.as_ref(),
+            b"=D0=9F=D1=80=D0=B8=D0=B2=D0=B5=D1=82, =D0=BC=D0=B8=D1=80!".as_ref()
+        );
+    }
+
+    #[test]
+    fn quoted_printable_encode_ascii() {
+        let encoded = Body::new_with_encoding(
+            String::from("Hello, world!"),
+            ContentTransferEncoding::QuotedPrintable,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::QuotedPrintable);
+        assert_eq!(encoded.as_ref(), b"Hello, world!");
+    }
+
+    #[test]
+    fn quoted_printable_encode_utf8() {
+        let encoded = Body::new_with_encoding(
+            String::from("Привет, мир!"),
+            ContentTransferEncoding::QuotedPrintable,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::QuotedPrintable);
+        assert_eq!(
+            encoded.as_ref(),
+            b"=D0=9F=D1=80=D0=B8=D0=B2=D0=B5=D1=82, =D0=BC=D0=B8=D1=80!".as_ref()
+        );
+    }
+
+    #[test]
+    fn quoted_printable_encode_line_wrap() {
+        let encoded = Body::new(String::from("Текст письма в уникоде"));
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::QuotedPrintable);
+        assert_eq!(
+            encoded.as_ref(),
+            concat!(
+                "=D0=A2=D0=B5=D0=BA=D1=81=D1=82 =D0=BF=D0=B8=D1=81=D1=8C=D0=BC=D0=B0 =D0=B2 =\r\n",
+                "=D1=83=D0=BD=D0=B8=D0=BA=D0=BE=D0=B4=D0=B5"
+            )
+            .as_bytes()
+        );
+    }
+
+    #[test]
+    fn base64_detect() {
+        let input = Body::new(vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+        let encoding = input.encoding();
+        assert_eq!(encoding, ContentTransferEncoding::Base64);
+    }
+
+    #[test]
+    fn base64_encode_bytes() {
+        let encoded = Body::new_with_encoding(
+            vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+            ContentTransferEncoding::Base64,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::Base64);
+        assert_eq!(encoded.as_ref(), b"AAECAwQFBgcICQ==");
+    }
+
+    #[test]
+    fn base64_encode_bytes_wrapping() {
+        let encoded = Body::new_with_encoding(
+            vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9].repeat(20),
+            ContentTransferEncoding::Base64,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::Base64);
+        assert_eq!(
+            encoded.as_ref(),
+            concat!(
+                "AAECAwQFBgcICQABAgMEBQYHCAkAAQIDBAUGBwgJAAECAwQFBgcICQABAgMEBQYHCAkAAQIDBAUG\r\n",
+                "BwgJAAECAwQFBgcICQABAgMEBQYHCAkAAQIDBAUGBwgJAAECAwQFBgcICQABAgMEBQYHCAkAAQID\r\n",
+                "BAUGBwgJAAECAwQFBgcICQABAgMEBQYHCAkAAQIDBAUGBwgJAAECAwQFBgcICQABAgMEBQYHCAkA\r\n",
+                "AQIDBAUGBwgJAAECAwQFBgcICQABAgMEBQYHCAk="
+            )
+            .as_bytes()
+        );
+    }
+
+    #[test]
+    fn base64_encode_ascii() {
+        let encoded = Body::new_with_encoding(
+            String::from("Hello World!"),
+            ContentTransferEncoding::Base64,
+        )
+        .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::Base64);
+        assert_eq!(encoded.as_ref(), b"SGVsbG8gV29ybGQh");
+    }
+
+    #[test]
+    fn base64_encode_ascii_wrapping() {
+        let encoded =
+            Body::new_with_encoding("Hello World!".repeat(20), ContentTransferEncoding::Base64)
+                .unwrap();
+
+        assert_eq!(encoded.encoding(), ContentTransferEncoding::Base64);
+        assert_eq!(
+            encoded.as_ref(),
+            concat!(
+                "SGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29y\r\n",
+                "bGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8g\r\n",
+                "V29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVs\r\n",
+                "bG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQhSGVsbG8gV29ybGQh\r\n",
+                "SGVsbG8gV29ybGQh"
+            )
+            .as_bytes()
+        );
+    }
+}

src/message/header/content.rs

@@ -0,0 +1,129 @@
+use hyperx::{
+    header::{Formatter as HeaderFormatter, Header, RawLike},
+    Error as HeaderError, Result as HyperResult,
+};
+use std::{
+    fmt::{Display, Formatter as FmtFormatter, Result as FmtResult},
+    str::{from_utf8, FromStr},
+};
+
+header! {
+    /// `Content-Id` header, defined in [RFC2045](https://tools.ietf.org/html/rfc2045#section-7)
+    (ContentId, "Content-ID") => [String]
+}
+
+/// `Content-Transfer-Encoding` of the body
+///
+/// The `Message` builder takes care of choosing the most
+/// efficient encoding based on the chosen body, so in most
+/// use-caches this header shouldn't be set manually.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum ContentTransferEncoding {
+    SevenBit,
+    QuotedPrintable,
+    Base64,
+    // 8BITMIME
+    EightBit,
+    Binary,
+}
+
+impl Default for ContentTransferEncoding {
+    fn default() -> Self {
+        ContentTransferEncoding::Base64
+    }
+}
+
+impl Display for ContentTransferEncoding {
+    fn fmt(&self, f: &mut FmtFormatter<'_>) -> FmtResult {
+        f.write_str(match *self {
+            Self::SevenBit => "7bit",
+            Self::QuotedPrintable => "quoted-printable",
+            Self::Base64 => "base64",
+            Self::EightBit => "8bit",
+            Self::Binary => "binary",
+        })
+    }
+}
+
+impl FromStr for ContentTransferEncoding {
+    type Err = String;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "7bit" => Ok(Self::SevenBit),
+            "quoted-printable" => Ok(Self::QuotedPrintable),
+            "base64" => Ok(Self::Base64),
+            "8bit" => Ok(Self::EightBit),
+            "binary" => Ok(Self::Binary),
+            _ => Err(s.into()),
+        }
+    }
+}
+
+impl Header for ContentTransferEncoding {
+    fn header_name() -> &'static str {
+        "Content-Transfer-Encoding"
+    }
+
+    // FIXME HeaderError->HeaderError, same for result
+    fn parse_header<'a, T>(raw: &'a T) -> HyperResult<Self>
+    where
+        T: RawLike<'a>,
+        Self: Sized,
+    {
+        raw.one()
+            .ok_or(HeaderError::Header)
+            .and_then(|r| from_utf8(r).map_err(|_| HeaderError::Header))
+            .and_then(|s| {
+                s.parse::<ContentTransferEncoding>()
+                    .map_err(|_| HeaderError::Header)
+            })
+    }
+
+    fn fmt_header(&self, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+        f.fmt_line(&format!("{}", self))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::ContentTransferEncoding;
+    use hyperx::header::Headers;
+
+    #[test]
+    fn format_content_transfer_encoding() {
+        let mut headers = Headers::new();
+
+        headers.set(ContentTransferEncoding::SevenBit);
+
+        assert_eq!(
+            format!("{}", headers),
+            "Content-Transfer-Encoding: 7bit\r\n"
+        );
+
+        headers.set(ContentTransferEncoding::Base64);
+
+        assert_eq!(
+            format!("{}", headers),
+            "Content-Transfer-Encoding: base64\r\n"
+        );
+    }
+
+    #[test]
+    fn parse_content_transfer_encoding() {
+        let mut headers = Headers::new();
+
+        headers.set_raw("Content-Transfer-Encoding", "7bit");
+
+        assert_eq!(
+            headers.get::<ContentTransferEncoding>(),
+            Some(&ContentTransferEncoding::SevenBit)
+        );
+
+        headers.set_raw("Content-Transfer-Encoding", "base64");
+
+        assert_eq!(
+            headers.get::<ContentTransferEncoding>(),
+            Some(&ContentTransferEncoding::Base64)
+        );
+    }
+}

src/message/header/mailbox.rs

@@ -0,0 +1,289 @@
+use crate::message::{
+    mailbox::{Mailbox, Mailboxes},
+    utf8_b,
+};
+use hyperx::{
+    header::{Formatter as HeaderFormatter, Header, RawLike},
+    Error as HeaderError, Result as HyperResult,
+};
+use std::{fmt::Result as FmtResult, slice::Iter, str::from_utf8};
+
+/// Header which can contains multiple mailboxes
+pub trait MailboxesHeader {
+    fn join_mailboxes(&mut self, other: Self);
+}
+
+macro_rules! mailbox_header {
+    ($(#[$doc:meta])*($type_name: ident, $header_name: expr)) => {
+        $(#[$doc])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub struct $type_name(pub Mailbox);
+
+        impl Header for $type_name {
+            fn header_name() -> &'static str {
+                $header_name
+            }
+
+            fn parse_header<'a, T>(raw: &'a T) -> HyperResult<Self> where
+    T: RawLike<'a>,
+    Self: Sized {
+                raw.one()
+                    .ok_or(HeaderError::Header)
+                    .and_then(parse_mailboxes)
+                    .and_then(|mbs| {
+                        mbs.into_single().ok_or(HeaderError::Header)
+                    }).map($type_name)
+            }
+
+            fn fmt_header(&self, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+                f.fmt_line(&self.0.recode_name(utf8_b::encode))
+            }
+        }
+    };
+}
+
+macro_rules! mailboxes_header {
+    ($(#[$doc:meta])*($type_name: ident, $header_name: expr)) => {
+        $(#[$doc])*
+        #[derive(Debug, Clone, PartialEq)]
+        pub struct $type_name(pub Mailboxes);
+
+        impl MailboxesHeader for $type_name {
+            fn join_mailboxes(&mut self, other: Self) {
+                self.0.extend(other.0);
+            }
+        }
+
+        impl Header for $type_name {
+            fn header_name() -> &'static str {
+                $header_name
+            }
+
+            fn parse_header<'a, T>(raw: &'a T) -> HyperResult<$type_name>
+            where
+                T: RawLike<'a>,
+                Self: Sized,
+            {
+                raw.one()
+                    .ok_or(HeaderError::Header)
+                    .and_then(parse_mailboxes)
+                    .map($type_name)
+            }
+
+            fn fmt_header(&self, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+                format_mailboxes(self.0.iter(), f)
+            }
+        }
+    };
+}
+
+mailbox_header! {
+    /**
+
+    `Sender` header
+
+    This header contains [`Mailbox`][self::Mailbox] associated with sender.
+
+    ```no_test
+    header::Sender("Mr. Sender <sender@example.com>".parse().unwrap())
+    ```
+     */
+    (Sender, "Sender")
+}
+
+mailboxes_header! {
+    /**
+
+    `From` header
+
+    This header contains [`Mailboxes`][self::Mailboxes].
+
+     */
+    (From, "From")
+}
+
+mailboxes_header! {
+    /**
+
+    `Reply-To` header
+
+    This header contains [`Mailboxes`][self::Mailboxes].
+
+     */
+    (ReplyTo, "Reply-To")
+}
+
+mailboxes_header! {
+    /**
+
+    `To` header
+
+    This header contains [`Mailboxes`][self::Mailboxes].
+
+     */
+    (To, "To")
+}
+
+mailboxes_header! {
+    /**
+
+    `Cc` header
+
+    This header contains [`Mailboxes`][self::Mailboxes].
+
+     */
+    (Cc, "Cc")
+}
+
+mailboxes_header! {
+    /**
+
+    `Bcc` header
+
+    This header contains [`Mailboxes`][self::Mailboxes].
+
+     */
+    (Bcc, "Bcc")
+}
+
+fn parse_mailboxes(raw: &[u8]) -> HyperResult<Mailboxes> {
+    if let Ok(src) = from_utf8(raw) {
+        if let Ok(mbs) = src.parse() {
+            return Ok(mbs);
+        }
+    }
+    Err(HeaderError::Header)
+}
+
+fn format_mailboxes<'a>(mbs: Iter<'a, Mailbox>, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+    f.fmt_line(&Mailboxes::from(
+        mbs.map(|mb| mb.recode_name(utf8_b::encode))
+            .collect::<Vec<_>>(),
+    ))
+}
+
+#[cfg(test)]
+mod test {
+    use super::{From, Mailbox, Mailboxes};
+    use hyperx::header::Headers;
+
+    #[test]
+    fn format_single_without_name() {
+        let from = Mailboxes::new().with("kayo@example.com".parse().unwrap());
+
+        let mut headers = Headers::new();
+        headers.set(From(from));
+
+        assert_eq!(format!("{}", headers), "From: kayo@example.com\r\n");
+    }
+
+    #[test]
+    fn format_single_with_name() {
+        let from = Mailboxes::new().with("K. <kayo@example.com>".parse().unwrap());
+
+        let mut headers = Headers::new();
+        headers.set(From(from));
+
+        assert_eq!(format!("{}", headers), "From: K. <kayo@example.com>\r\n");
+    }
+
+    #[test]
+    fn format_multi_without_name() {
+        let from = Mailboxes::new()
+            .with("kayo@example.com".parse().unwrap())
+            .with("pony@domain.tld".parse().unwrap());
+
+        let mut headers = Headers::new();
+        headers.set(From(from));
+
+        assert_eq!(
+            format!("{}", headers),
+            "From: kayo@example.com, pony@domain.tld\r\n"
+        );
+    }
+
+    #[test]
+    fn format_multi_with_name() {
+        let from = vec![
+            "K. <kayo@example.com>".parse().unwrap(),
+            "Pony P. <pony@domain.tld>".parse().unwrap(),
+        ];
+
+        let mut headers = Headers::new();
+        headers.set(From(from.into()));
+
+        assert_eq!(
+            format!("{}", headers),
+            "From: K. <kayo@example.com>, Pony P. <pony@domain.tld>\r\n"
+        );
+    }
+
+    #[test]
+    fn format_single_with_utf8_name() {
+        let from = vec!["Кайо <kayo@example.com>".parse().unwrap()];
+
+        let mut headers = Headers::new();
+        headers.set(From(from.into()));
+
+        assert_eq!(
+            format!("{}", headers),
+            "From: =?utf-8?b?0JrQsNC50L4=?= <kayo@example.com>\r\n"
+        );
+    }
+
+    #[test]
+    fn parse_single_without_name() {
+        let from = vec!["kayo@example.com".parse().unwrap()].into();
+
+        let mut headers = Headers::new();
+        headers.set_raw("From", "kayo@example.com");
+
+        assert_eq!(headers.get::<From>(), Some(&From(from)));
+    }
+
+    #[test]
+    fn parse_single_with_name() {
+        let from = vec!["K. <kayo@example.com>".parse().unwrap()].into();
+
+        let mut headers = Headers::new();
+        headers.set_raw("From", "K. <kayo@example.com>");
+
+        assert_eq!(headers.get::<From>(), Some(&From(from)));
+    }
+
+    #[test]
+    fn parse_multi_without_name() {
+        let from: Vec<Mailbox> = vec![
+            "kayo@example.com".parse().unwrap(),
+            "pony@domain.tld".parse().unwrap(),
+        ];
+
+        let mut headers = Headers::new();
+        headers.set_raw("From", "kayo@example.com, pony@domain.tld");
+
+        assert_eq!(headers.get::<From>(), Some(&From(from.into())));
+    }
+
+    #[test]
+    fn parse_multi_with_name() {
+        let from: Vec<Mailbox> = vec![
+            "K. <kayo@example.com>".parse().unwrap(),
+            "Pony P. <pony@domain.tld>".parse().unwrap(),
+        ];
+
+        let mut headers = Headers::new();
+        headers.set_raw("From", "K. <kayo@example.com>, Pony P. <pony@domain.tld>");
+
+        assert_eq!(headers.get::<From>(), Some(&From(from.into())));
+    }
+
+    #[test]
+    fn parse_single_with_utf8_name() {
+        let from: Vec<Mailbox> = vec!["Кайо <kayo@example.com>".parse().unwrap()];
+
+        let mut headers = Headers::new();
+        headers.set_raw("From", "=?utf-8?b?0JrQsNC50L4=?= <kayo@example.com>");
+
+        assert_eq!(headers.get::<From>(), Some(&From(from.into())));
+    }
+}

src/message/header/mod.rs

@@ -0,0 +1,13 @@
+//! Headers widely used in email messages
+
+mod content;
+mod mailbox;
+mod special;
+mod textual;
+
+pub use self::{content::*, mailbox::*, special::*, textual::*};
+
+pub use hyperx::header::{
+    Charset, ContentDisposition, ContentLocation, ContentType, Date, DispositionParam,
+    DispositionType, Header, Headers, HttpDate as EmailDate,
+};

src/message/header/special.rs

@@ -0,0 +1,84 @@
+use hyperx::{
+    header::{Formatter as HeaderFormatter, Header, RawLike},
+    Error as HeaderError, Result as HyperResult,
+};
+use std::{fmt::Result as FmtResult, str::from_utf8};
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+/// Message format version, defined in [RFC2045](https://tools.ietf.org/html/rfc2045#section-4)
+pub struct MimeVersion {
+    pub major: u8,
+    pub minor: u8,
+}
+
+pub const MIME_VERSION_1_0: MimeVersion = MimeVersion { major: 1, minor: 0 };
+
+impl MimeVersion {
+    pub fn new(major: u8, minor: u8) -> Self {
+        MimeVersion { major, minor }
+    }
+}
+
+impl Default for MimeVersion {
+    fn default() -> Self {
+        MIME_VERSION_1_0
+    }
+}
+
+impl Header for MimeVersion {
+    fn header_name() -> &'static str {
+        "MIME-Version"
+    }
+
+    fn parse_header<'a, T>(raw: &'a T) -> HyperResult<Self>
+    where
+        T: RawLike<'a>,
+        Self: Sized,
+    {
+        raw.one().ok_or(HeaderError::Header).and_then(|r| {
+            let mut s = from_utf8(r).map_err(|_| HeaderError::Header)?.split('.');
+
+            let major = s.next().ok_or(HeaderError::Header)?;
+            let minor = s.next().ok_or(HeaderError::Header)?;
+            let major = major.parse().map_err(|_| HeaderError::Header)?;
+            let minor = minor.parse().map_err(|_| HeaderError::Header)?;
+            Ok(MimeVersion::new(major, minor))
+        })
+    }
+
+    fn fmt_header(&self, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+        f.fmt_line(&format!("{}.{}", self.major, self.minor))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::{MimeVersion, MIME_VERSION_1_0};
+    use hyperx::header::Headers;
+
+    #[test]
+    fn format_mime_version() {
+        let mut headers = Headers::new();
+
+        headers.set(MIME_VERSION_1_0);
+
+        assert_eq!(format!("{}", headers), "MIME-Version: 1.0\r\n");
+
+        headers.set(MimeVersion::new(0, 1));
+
+        assert_eq!(format!("{}", headers), "MIME-Version: 0.1\r\n");
+    }
+
+    #[test]
+    fn parse_mime_version() {
+        let mut headers = Headers::new();
+
+        headers.set_raw("MIME-Version", "1.0");
+
+        assert_eq!(headers.get::<MimeVersion>(), Some(&MIME_VERSION_1_0));
+
+        headers.set_raw("MIME-Version", "0.1");
+
+        assert_eq!(headers.get::<MimeVersion>(), Some(&MimeVersion::new(0, 1)));
+    }
+}

src/message/header/textual.rs

@@ -0,0 +1,134 @@
+use crate::message::utf8_b;
+use hyperx::{
+    header::{Formatter as HeaderFormatter, Header, RawLike},
+    Error as HeaderError, Result as HyperResult,
+};
+use std::{fmt::Result as FmtResult, str::from_utf8};
+
+macro_rules! text_header {
+    ($(#[$attr:meta])* Header($type_name: ident, $header_name: expr )) => {
+        #[derive(Debug, Clone, PartialEq)]
+        $(#[$attr])*
+        pub struct $type_name(pub String);
+
+        impl Header for $type_name {
+            fn header_name() -> &'static str {
+                $header_name
+            }
+
+            fn parse_header<'a, T>(raw: &'a T) -> HyperResult<$type_name>
+            where
+                T: RawLike<'a>,
+                Self: Sized,
+            {
+                raw.one()
+                    .ok_or(HeaderError::Header)
+                    .and_then(parse_text)
+                    .map($type_name)
+            }
+
+            fn fmt_header(&self, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+                fmt_text(&self.0, f)
+            }
+        }
+    };
+}
+
+text_header!(
+    /// `Subject` of the message, defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.5)
+    Header(Subject, "Subject")
+);
+text_header!(
+    /// `Comments` of the message, defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.5)
+    Header(Comments, "Comments")
+);
+text_header!(
+    /// `Keywords` header. Should contain a comma-separated list of one or more
+    /// words or quoted-strings, defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.5)
+    Header(Keywords, "Keywords")
+);
+text_header!(
+    /// `In-Reply-To` header. Contains one or more
+    /// unique message identifiers,
+    /// defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.4)
+    Header(InReplyTo, "In-Reply-To")
+);
+text_header!(
+    /// `References` header. Contains one or more
+    /// unique message identifiers,
+    /// defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.4)
+    Header(References, "References")
+);
+text_header!(
+    /// `Message-Id` header. Contains a unique message identifier,
+    /// defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.4)
+    Header(MessageId, "Message-Id")
+);
+text_header!(
+    /// `User-Agent` header. Contains information about the client,
+    /// defined in [draft-melnikov-email-user-agent-00](https://tools.ietf.org/html/draft-melnikov-email-user-agent-00#section-3)
+    Header(UserAgent, "User-Agent")
+);
+
+fn parse_text(raw: &[u8]) -> HyperResult<String> {
+    if let Ok(src) = from_utf8(raw) {
+        if let Some(txt) = utf8_b::decode(src) {
+            return Ok(txt);
+        }
+    }
+    Err(HeaderError::Header)
+}
+
+fn fmt_text(s: &str, f: &mut HeaderFormatter<'_, '_>) -> FmtResult {
+    f.fmt_line(&utf8_b::encode(s))
+}
+
+#[cfg(test)]
+mod test {
+    use super::Subject;
+    use hyperx::header::Headers;
+
+    #[test]
+    fn format_ascii() {
+        let mut headers = Headers::new();
+        headers.set(Subject("Sample subject".into()));
+
+        assert_eq!(format!("{}", headers), "Subject: Sample subject\r\n");
+    }
+
+    #[test]
+    fn format_utf8() {
+        let mut headers = Headers::new();
+        headers.set(Subject("Тема сообщения".into()));
+
+        assert_eq!(
+            format!("{}", headers),
+            "Subject: =?utf-8?b?0KLQtdC80LAg0YHQvtC+0LHRidC10L3QuNGP?=\r\n"
+        );
+    }
+
+    #[test]
+    fn parse_ascii() {
+        let mut headers = Headers::new();
+        headers.set_raw("Subject", "Sample subject");
+
+        assert_eq!(
+            headers.get::<Subject>(),
+            Some(&Subject("Sample subject".into()))
+        );
+    }
+
+    #[test]
+    fn parse_utf8() {
+        let mut headers = Headers::new();
+        headers.set_raw(
+            "Subject",
+            "=?utf-8?b?0KLQtdC80LAg0YHQvtC+0LHRidC10L3QuNGP?=",
+        );
+
+        assert_eq!(
+            headers.get::<Subject>(),
+            Some(&Subject("Тема сообщения".into()))
+        );
+    }
+}

src/message/mailbox/mod.rs

@@ -0,0 +1,5 @@
+#[cfg(feature = "serde")]
+mod serde;
+mod types;
+
+pub use self::types::*;

src/message/mailbox/serde.rs

@@ -0,0 +1,215 @@
+use crate::message::{Mailbox, Mailboxes};
+use serde::{
+    de::{Deserializer, Error as DeError, MapAccess, SeqAccess, Visitor},
+    ser::Serializer,
+    Deserialize, Serialize,
+};
+use std::fmt::{Formatter, Result as FmtResult};
+
+impl Serialize for Mailbox {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(&self.to_string())
+    }
+}
+
+impl<'de> Deserialize<'de> for Mailbox {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        enum Field {
+            Name,
+            Email,
+        }
+
+        const FIELDS: &[&str] = &["name", "email"];
+
+        impl<'de> Deserialize<'de> for Field {
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+            where
+                D: Deserializer<'de>,
+            {
+                struct FieldVisitor;
+
+                impl<'de> Visitor<'de> for FieldVisitor {
+                    type Value = Field;
+
+                    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+                        formatter.write_str("'name' or 'email'")
+                    }
+
+                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
+                    where
+                        E: DeError,
+                    {
+                        match value {
+                            "name" => Ok(Field::Name),
+                            "email" => Ok(Field::Email),
+                            _ => Err(DeError::unknown_field(value, FIELDS)),
+                        }
+                    }
+                }
+
+                deserializer.deserialize_identifier(FieldVisitor)
+            }
+        }
+
+        struct MailboxVisitor;
+
+        impl<'de> Visitor<'de> for MailboxVisitor {
+            type Value = Mailbox;
+
+            fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+                formatter.write_str("mailbox string or object")
+            }
+
+            fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
+            where
+                E: DeError,
+            {
+                s.parse().map_err(DeError::custom)
+            }
+
+            fn visit_map<V>(self, mut map: V) -> Result<Self::Value, V::Error>
+            where
+                V: MapAccess<'de>,
+            {
+                let mut name = None;
+                let mut addr = None;
+                while let Some(key) = map.next_key()? {
+                    match key {
+                        Field::Name => {
+                            if name.is_some() {
+                                return Err(DeError::duplicate_field("name"));
+                            }
+                            name = Some(map.next_value()?);
+                        }
+                        Field::Email => {
+                            if addr.is_some() {
+                                return Err(DeError::duplicate_field("email"));
+                            }
+                            addr = Some(map.next_value()?);
+                        }
+                    }
+                }
+                let addr = addr.ok_or_else(|| DeError::missing_field("email"))?;
+                Ok(Mailbox::new(name, addr))
+            }
+        }
+
+        deserializer.deserialize_any(MailboxVisitor)
+    }
+}
+
+impl Serialize for Mailboxes {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(&self.to_string())
+    }
+}
+
+impl<'de> Deserialize<'de> for Mailboxes {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct MailboxesVisitor;
+
+        impl<'de> Visitor<'de> for MailboxesVisitor {
+            type Value = Mailboxes;
+
+            fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+                formatter.write_str("mailboxes string or sequence")
+            }
+
+            fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
+            where
+                E: DeError,
+            {
+                s.parse().map_err(DeError::custom)
+            }
+
+            fn visit_seq<V>(self, mut seq: V) -> Result<Self::Value, V::Error>
+            where
+                V: SeqAccess<'de>,
+            {
+                let mut mboxes = Mailboxes::new();
+                while let Some(mbox) = seq.next_element()? {
+                    mboxes.push(mbox);
+                }
+                Ok(mboxes)
+            }
+        }
+
+        deserializer.deserialize_any(MailboxesVisitor)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::address::Address;
+    use serde_json::from_str;
+
+    #[test]
+    fn parse_address_string() {
+        let m: Address = from_str(r#""kayo@example.com""#).unwrap();
+        assert_eq!(m, "kayo@example.com".parse().unwrap());
+    }
+
+    #[test]
+    fn parse_address_object() {
+        let m: Address = from_str(r#"{ "user": "kayo", "domain": "example.com" }"#).unwrap();
+        assert_eq!(m, "kayo@example.com".parse().unwrap());
+    }
+
+    #[test]
+    fn parse_mailbox_string() {
+        let m: Mailbox = from_str(r#""Kai <kayo@example.com>""#).unwrap();
+        assert_eq!(m, "Kai <kayo@example.com>".parse().unwrap());
+    }
+
+    #[test]
+    fn parse_mailbox_object_address_stirng() {
+        let m: Mailbox = from_str(r#"{ "name": "Kai", "email": "kayo@example.com" }"#).unwrap();
+        assert_eq!(m, "Kai <kayo@example.com>".parse().unwrap());
+    }
+
+    #[test]
+    fn parse_mailbox_object_address_object() {
+        let m: Mailbox =
+            from_str(r#"{ "name": "Kai", "email": { "user": "kayo", "domain": "example.com" } }"#)
+                .unwrap();
+        assert_eq!(m, "Kai <kayo@example.com>".parse().unwrap());
+    }
+
+    #[test]
+    fn parse_mailboxes_string() {
+        let m: Mailboxes =
+            from_str(r#""yin@dtb.com, Hei <hei@dtb.com>, Kai <kayo@example.com>""#).unwrap();
+        assert_eq!(
+            m,
+            "<yin@dtb.com>, Hei <hei@dtb.com>, Kai <kayo@example.com>"
+                .parse()
+                .unwrap()
+        );
+    }
+
+    #[test]
+    fn parse_mailboxes_array() {
+        let m: Mailboxes =
+            from_str(r#"["yin@dtb.com", { "name": "Hei", "email": "hei@dtb.com" }, { "name": "Kai", "email": { "user": "kayo", "domain": "example.com" } }]"#)
+                .unwrap();
+        assert_eq!(
+            m,
+            "<yin@dtb.com>, Hei <hei@dtb.com>, Kai <kayo@example.com>"
+                .parse()
+                .unwrap()
+        );
+    }
+}

src/message/mailbox/types.rs

@@ -0,0 +1,447 @@
+use crate::{
+    address::{Address, AddressError},
+    message::utf8_b,
+};
+use std::{
+    convert::TryFrom,
+    fmt::{Display, Formatter, Result as FmtResult, Write},
+    slice::Iter,
+    str::FromStr,
+};
+
+/// Represents an email address with an optional name for the sender/recipient.
+///
+/// This type contains email address and the sender/recipient name (_Some Name \<user@domain.tld\>_ or _withoutname@domain.tld_).
+///
+/// **NOTE**: Enable feature "serde" to be able serialize/deserialize it using [serde](https://serde.rs/).
+///
+/// # Examples
+///
+/// You can create a `Mailbox` from a string and an [`Address`]:
+///
+/// ```
+/// # use lettre::{Address, message::Mailbox};
+/// # use std::error::Error;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let address = Address::new("example", "email.com")?;
+/// let mailbox = Mailbox::new(None, address);
+/// # Ok(())
+/// # }
+/// ```
+///
+/// You can also create one from a string literal:
+///
+/// ```
+/// # use lettre::message::Mailbox;
+/// # use std::error::Error;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let mailbox: Mailbox = "John Smith <example@email.com>".parse()?;
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Debug, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
+pub struct Mailbox {
+    /// The name associated with the address.
+    pub name: Option<String>,
+
+    /// The email address itself.
+    pub email: Address,
+}
+
+impl Mailbox {
+    /// Creates a new `Mailbox` using an email address and the name of the recipient if there is one.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::{message::Mailbox, Address};
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let address = Address::new("example", "email.com")?;
+    /// let mailbox = Mailbox::new(None, address);
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn new(name: Option<String>, email: Address) -> Self {
+        Mailbox { name, email }
+    }
+
+    /// Encode addressee name using function
+    pub(crate) fn recode_name<F>(&self, f: F) -> Self
+    where
+        F: FnOnce(&str) -> String,
+    {
+        Mailbox::new(self.name.clone().map(|s| f(&s)), self.email.clone())
+    }
+}
+
+impl Display for Mailbox {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        if let Some(ref name) = self.name {
+            let name = name.trim();
+            if !name.is_empty() {
+                f.write_str(&name)?;
+                f.write_str(" <")?;
+                self.email.fmt(f)?;
+                return f.write_char('>');
+            }
+        }
+        self.email.fmt(f)
+    }
+}
+
+impl<S: Into<String>, T: Into<String>> TryFrom<(S, T)> for Mailbox {
+    type Error = AddressError;
+
+    fn try_from(header: (S, T)) -> Result<Self, Self::Error> {
+        let (name, address) = header;
+        Ok(Mailbox::new(Some(name.into()), address.into().parse()?))
+    }
+}
+
+/*
+impl<S: AsRef<&str>, T: AsRef<&str>> TryFrom<(S, T)> for Mailbox {
+    type Error = AddressError;
+
+    fn try_from(header: (S, T)) -> Result<Self, Self::Error> {
+        let (name, address) = header;
+        Ok(Mailbox::new(Some(name.as_ref()), address.as_ref().parse()?))
+    }
+}*/
+
+impl FromStr for Mailbox {
+    type Err = AddressError;
+
+    fn from_str(src: &str) -> Result<Mailbox, Self::Err> {
+        match (src.find('<'), src.find('>')) {
+            (Some(addr_open), Some(addr_close)) if addr_open < addr_close => {
+                let name = src.split_at(addr_open).0;
+                let addr_open = addr_open + 1;
+                let addr = src.split_at(addr_open).1.split_at(addr_close - addr_open).0;
+                let addr = addr.parse()?;
+                let name = name.trim();
+                let name = if name.is_empty() {
+                    None
+                } else {
+                    Some(name.into())
+                };
+                Ok(Mailbox::new(name, addr))
+            }
+            (Some(_), _) => Err(AddressError::Unbalanced),
+            _ => {
+                let addr = src.parse()?;
+                Ok(Mailbox::new(None, addr))
+            }
+        }
+    }
+}
+
+/// Represents a sequence of [`Mailbox`] instances.
+///
+/// This type contains a sequence of mailboxes (_Some Name \<user@domain.tld\>, Another Name \<other@domain.tld\>, withoutname@domain.tld, ..._).
+///
+/// **NOTE**: Enable feature "serde" to be able serialize/deserialize it using [serde](https://serde.rs/).
+#[derive(Debug, Clone, PartialOrd, Ord, PartialEq, Eq, Hash)]
+pub struct Mailboxes(Vec<Mailbox>);
+
+impl Mailboxes {
+    /// Creates a new list of [`Mailbox`] instances.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::message::Mailboxes;
+    /// let mailboxes = Mailboxes::new();
+    /// ```
+    pub fn new() -> Self {
+        Mailboxes(Vec::new())
+    }
+
+    /// Adds a new [`Mailbox`] to the list, in a builder style pattern.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let address = Address::new("example", "email.com")?;
+    /// let mut mailboxes = Mailboxes::new().with(Mailbox::new(None, address));
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn with(mut self, mbox: Mailbox) -> Self {
+        self.0.push(mbox);
+        self
+    }
+
+    /// Adds a new [`Mailbox`] to the list, in a Vec::push style pattern.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let address = Address::new("example", "email.com")?;
+    /// let mut mailboxes = Mailboxes::new();
+    /// mailboxes.push(Mailbox::new(None, address));
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn push(&mut self, mbox: Mailbox) {
+        self.0.push(mbox);
+    }
+
+    /// Extracts the first [`Mailbox`] if it exists.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let empty = Mailboxes::new();
+    /// assert!(empty.into_single().is_none());
+    ///
+    /// let mut mailboxes = Mailboxes::new();
+    /// let address = Address::new("example", "email.com")?;
+    ///
+    /// mailboxes.push(Mailbox::new(None, address));
+    /// assert!(mailboxes.into_single().is_some());
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn into_single(self) -> Option<Mailbox> {
+        self.into()
+    }
+
+    /// Creates an iterator over the [`Mailbox`] instances that are currently stored.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
+    ///
+    /// # use std::error::Error;
+    /// # fn main() -> Result<(), Box<dyn Error>> {
+    /// let mut mailboxes = Mailboxes::new();
+    ///
+    /// let address = Address::new("example", "email.com")?;
+    /// mailboxes.push(Mailbox::new(None, address));
+    ///
+    /// let address = Address::new("example", "email.com")?;
+    /// mailboxes.push(Mailbox::new(None, address));
+    ///
+    /// let mut iter = mailboxes.iter();
+    ///
+    /// assert!(iter.next().is_some());
+    /// assert!(iter.next().is_some());
+    ///
+    /// assert!(iter.next().is_none());
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn iter(&self) -> Iter<'_, Mailbox> {
+        self.0.iter()
+    }
+}
+
+impl Default for Mailboxes {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl From<Mailbox> for Mailboxes {
+    fn from(mailbox: Mailbox) -> Self {
+        Mailboxes(vec![mailbox])
+    }
+}
+
+impl From<Mailboxes> for Option<Mailbox> {
+    fn from(mailboxes: Mailboxes) -> Option<Mailbox> {
+        mailboxes.into_iter().next()
+    }
+}
+
+impl From<Vec<Mailbox>> for Mailboxes {
+    fn from(vec: Vec<Mailbox>) -> Self {
+        Mailboxes(vec)
+    }
+}
+
+impl From<Mailboxes> for Vec<Mailbox> {
+    fn from(mailboxes: Mailboxes) -> Vec<Mailbox> {
+        mailboxes.0
+    }
+}
+
+impl IntoIterator for Mailboxes {
+    type Item = Mailbox;
+    type IntoIter = ::std::vec::IntoIter<Mailbox>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+impl Extend<Mailbox> for Mailboxes {
+    fn extend<T: IntoIterator<Item = Mailbox>>(&mut self, iter: T) {
+        for elem in iter {
+            self.0.push(elem);
+        }
+    }
+}
+
+impl Display for Mailboxes {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        let mut iter = self.iter();
+
+        if let Some(mbox) = iter.next() {
+            mbox.fmt(f)?;
+
+            for mbox in iter {
+                f.write_str(", ")?;
+                mbox.fmt(f)?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl FromStr for Mailboxes {
+    type Err = AddressError;
+
+    fn from_str(src: &str) -> Result<Self, Self::Err> {
+        src.split(',')
+            .map(|m| {
+                m.trim().parse().and_then(|Mailbox { name, email }| {
+                    if let Some(name) = name {
+                        if let Some(name) = utf8_b::decode(&name) {
+                            Ok(Mailbox::new(Some(name), email))
+                        } else {
+                            Err(AddressError::InvalidUtf8b)
+                        }
+                    } else {
+                        Ok(Mailbox::new(None, email))
+                    }
+                })
+            })
+            .collect::<Result<Vec<_>, _>>()
+            .map(Mailboxes)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Mailbox;
+    use std::convert::TryInto;
+
+    #[test]
+    fn mailbox_format_address_only() {
+        assert_eq!(
+            format!(
+                "{}",
+                Mailbox::new(None, "kayo@example.com".parse().unwrap())
+            ),
+            "kayo@example.com"
+        );
+    }
+
+    #[test]
+    fn mailbox_format_address_with_name() {
+        assert_eq!(
+            format!(
+                "{}",
+                Mailbox::new(Some("K.".into()), "kayo@example.com".parse().unwrap())
+            ),
+            "K. <kayo@example.com>"
+        );
+    }
+
+    #[test]
+    fn format_address_with_empty_name() {
+        assert_eq!(
+            format!(
+                "{}",
+                Mailbox::new(Some("".into()), "kayo@example.com".parse().unwrap())
+            ),
+            "kayo@example.com"
+        );
+    }
+
+    #[test]
+    fn format_address_with_name_trim() {
+        assert_eq!(
+            format!(
+                "{}",
+                Mailbox::new(Some(" K. ".into()), "kayo@example.com".parse().unwrap())
+            ),
+            "K. <kayo@example.com>"
+        );
+    }
+
+    #[test]
+    fn parse_address_only() {
+        assert_eq!(
+            "kayo@example.com".parse(),
+            Ok(Mailbox::new(None, "kayo@example.com".parse().unwrap()))
+        );
+    }
+
+    #[test]
+    fn parse_address_with_name() {
+        assert_eq!(
+            "K. <kayo@example.com>".parse(),
+            Ok(Mailbox::new(
+                Some("K.".into()),
+                "kayo@example.com".parse().unwrap()
+            ))
+        );
+    }
+
+    #[test]
+    fn parse_address_with_empty_name() {
+        assert_eq!(
+            "<kayo@example.com>".parse(),
+            Ok(Mailbox::new(None, "kayo@example.com".parse().unwrap()))
+        );
+    }
+
+    #[test]
+    fn parse_address_with_empty_name_trim() {
+        assert_eq!(
+            " <kayo@example.com>".parse(),
+            Ok(Mailbox::new(None, "kayo@example.com".parse().unwrap()))
+        );
+    }
+
+    #[test]
+    fn parse_address_from_tuple() {
+        assert_eq!(
+            ("K.".to_string(), "kayo@example.com".to_string()).try_into(),
+            Ok(Mailbox::new(
+                Some("K.".into()),
+                "kayo@example.com".parse().unwrap()
+            ))
+        );
+    }
+}

src/message/mimebody.rs

@@ -0,0 +1,746 @@
+use crate::message::{
+    header::{ContentTransferEncoding, ContentType, Header, Headers},
+    EmailFormat, IntoBody,
+};
+use mime::Mime;
+use rand::Rng;
+
+/// MIME part variants
+#[derive(Debug, Clone)]
+pub enum Part {
+    /// Single part with content
+    Single(SinglePart),
+
+    /// Multiple parts of content
+    Multi(MultiPart),
+}
+
+impl EmailFormat for Part {
+    fn format(&self, out: &mut Vec<u8>) {
+        match self {
+            Part::Single(part) => part.format(out),
+            Part::Multi(part) => part.format(out),
+        }
+    }
+}
+
+impl Part {
+    /// Get message content formatted for SMTP
+    pub fn formatted(&self) -> Vec<u8> {
+        let mut out = Vec::new();
+        self.format(&mut out);
+        out
+    }
+}
+
+/// Parts of multipart body
+pub type Parts = Vec<Part>;
+
+/// Creates builder for single part
+#[derive(Debug, Clone)]
+pub struct SinglePartBuilder {
+    headers: Headers,
+}
+
+impl SinglePartBuilder {
+    /// Creates a default singlepart builder
+    pub fn new() -> Self {
+        Self {
+            headers: Headers::new(),
+        }
+    }
+
+    /// Set the header to singlepart
+    pub fn header<H: Header>(mut self, header: H) -> Self {
+        self.headers.set(header);
+        self
+    }
+
+    /// Set the Content-Type header of the singlepart
+    pub fn content_type(mut self, content_type: ContentType) -> Self {
+        self.headers.set(content_type);
+        self
+    }
+
+    /// Build singlepart using body
+    pub fn body<T: IntoBody>(mut self, body: T) -> SinglePart {
+        let maybe_encoding = self.headers.get::<ContentTransferEncoding>().copied();
+        let body = body.into_body(maybe_encoding);
+
+        self.headers.set(body.encoding());
+
+        SinglePart {
+            headers: self.headers,
+            body: body.into_vec(),
+        }
+    }
+}
+
+impl Default for SinglePartBuilder {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Single part
+///
+/// # Example
+///
+/// ```
+/// use lettre::message::{header, SinglePart};
+///
+/// # use std::error::Error;
+/// # fn main() -> Result<(), Box<dyn Error>> {
+/// let part = SinglePart::builder()
+///     .header(header::ContentType("text/plain; charset=utf8".parse()?))
+///     .body(String::from("Текст письма в уникоде"));
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Debug, Clone)]
+pub struct SinglePart {
+    headers: Headers,
+    body: Vec<u8>,
+}
+
+impl SinglePart {
+    /// Creates a builder for singlepart
+    #[inline]
+    pub fn builder() -> SinglePartBuilder {
+        SinglePartBuilder::new()
+    }
+
+    /// Get the headers from singlepart
+    #[inline]
+    pub fn headers(&self) -> &Headers {
+        &self.headers
+    }
+
+    /// Get the encoded body
+    #[inline]
+    pub fn raw_body(&self) -> &[u8] {
+        &self.body
+    }
+
+    /// Get message content formatted for sending
+    pub fn formatted(&self) -> Vec<u8> {
+        let mut out = Vec::new();
+        self.format(&mut out);
+        out
+    }
+}
+
+impl EmailFormat for SinglePart {
+    fn format(&self, out: &mut Vec<u8>) {
+        out.extend_from_slice(self.headers.to_string().as_bytes());
+        out.extend_from_slice(b"\r\n");
+        out.extend_from_slice(&self.body);
+        out.extend_from_slice(b"\r\n");
+    }
+}
+
+/// The kind of multipart
+#[derive(Debug, Clone)]
+pub enum MultiPartKind {
+    /// Mixed kind to combine unrelated content parts
+    ///
+    /// For example this kind can be used to mix email message and attachments.
+    Mixed,
+
+    /// Alternative kind to join several variants of same email contents.
+    ///
+    /// That kind is recommended to use for joining plain (text) and rich (HTML) messages into single email message.
+    Alternative,
+
+    /// Related kind to mix content and related resources.
+    ///
+    /// For example, you can include images into HTML content using that.
+    Related,
+
+    /// Encrypted kind for encrypted messages
+    Encrypted { protocol: String },
+
+    /// Signed kind for signed messages
+    Signed { protocol: String, micalg: String },
+}
+
+/// Create a random MIME boundary.
+fn make_boundary() -> String {
+    rand::thread_rng()
+        .sample_iter(rand::distributions::Alphanumeric)
+        .take(40)
+        .map(char::from)
+        .collect()
+}
+
+impl MultiPartKind {
+    fn to_mime<S: Into<String>>(&self, boundary: Option<S>) -> Mime {
+        let boundary = boundary.map_or_else(make_boundary, |s| s.into());
+
+        use self::MultiPartKind::*;
+        format!(
+            "multipart/{}; boundary=\"{}\"{}",
+            match self {
+                Mixed => "mixed",
+                Alternative => "alternative",
+                Related => "related",
+                Encrypted { .. } => "encrypted",
+                Signed { .. } => "signed",
+            },
+            boundary,
+            match self {
+                Encrypted { protocol } => format!("; protocol=\"{}\"", protocol),
+                Signed { protocol, micalg } =>
+                    format!("; protocol=\"{}\"; micalg=\"{}\"", protocol, micalg),
+                _ => String::new(),
+            }
+        )
+        .parse()
+        .unwrap()
+    }
+
+    fn from_mime(m: &Mime) -> Option<Self> {
+        use self::MultiPartKind::*;
+        match m.subtype().as_ref() {
+            "mixed" => Some(Mixed),
+            "alternative" => Some(Alternative),
+            "related" => Some(Related),
+            "signed" => m.get_param("protocol").and_then(|p| {
+                m.get_param("micalg").map(|micalg| Signed {
+                    protocol: p.as_str().to_owned(),
+                    micalg: micalg.as_str().to_owned(),
+                })
+            }),
+            "encrypted" => m.get_param("protocol").map(|p| Encrypted {
+                protocol: p.as_str().to_owned(),
+            }),
+            _ => None,
+        }
+    }
+}
+
+impl From<MultiPartKind> for Mime {
+    fn from(m: MultiPartKind) -> Self {
+        m.to_mime::<String>(None)
+    }
+}
+
+/// Multipart builder
+#[derive(Debug, Clone)]
+pub struct MultiPartBuilder {
+    headers: Headers,
+}
+
+impl MultiPartBuilder {
+    /// Creates default multipart builder
+    pub fn new() -> Self {
+        Self {
+            headers: Headers::new(),
+        }
+    }
+
+    /// Set a header
+    pub fn header<H: Header>(mut self, header: H) -> Self {
+        self.headers.set(header);
+        self
+    }
+
+    /// Set `Content-Type` header using [`MultiPartKind`]
+    pub fn kind(self, kind: MultiPartKind) -> Self {
+        self.header(ContentType(kind.into()))
+    }
+
+    /// Set custom boundary
+    pub fn boundary<S: AsRef<str>>(self, boundary: S) -> Self {
+        let kind = {
+            let mime = &self.headers.get::<ContentType>().unwrap().0;
+            MultiPartKind::from_mime(mime).unwrap()
+        };
+        let mime = kind.to_mime(Some(boundary.as_ref()));
+        self.header(ContentType(mime))
+    }
+
+    /// Creates multipart without parts
+    pub fn build(self) -> MultiPart {
+        MultiPart {
+            headers: self.headers,
+            parts: Vec::new(),
+        }
+    }
+
+    /// Creates multipart using part
+    pub fn part(self, part: Part) -> MultiPart {
+        self.build().part(part)
+    }
+
+    /// Creates multipart using singlepart
+    pub fn singlepart(self, part: SinglePart) -> MultiPart {
+        self.build().singlepart(part)
+    }
+
+    /// Creates multipart using multipart
+    pub fn multipart(self, part: MultiPart) -> MultiPart {
+        self.build().multipart(part)
+    }
+}
+
+impl Default for MultiPartBuilder {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Multipart variant with parts
+#[derive(Debug, Clone)]
+pub struct MultiPart {
+    headers: Headers,
+    parts: Parts,
+}
+
+impl MultiPart {
+    /// Creates multipart builder
+    pub fn builder() -> MultiPartBuilder {
+        MultiPartBuilder::new()
+    }
+
+    /// Creates mixed multipart builder
+    ///
+    /// Shortcut for `MultiPart::builder().kind(MultiPartKind::Mixed)`
+    pub fn mixed() -> MultiPartBuilder {
+        MultiPart::builder().kind(MultiPartKind::Mixed)
+    }
+
+    /// Creates alternative multipart builder
+    ///
+    /// Shortcut for `MultiPart::builder().kind(MultiPartKind::Alternative)`
+    pub fn alternative() -> MultiPartBuilder {
+        MultiPart::builder().kind(MultiPartKind::Alternative)
+    }
+
+    /// Creates related multipart builder
+    ///
+    /// Shortcut for `MultiPart::builder().kind(MultiPartKind::Related)`
+    pub fn related() -> MultiPartBuilder {
+        MultiPart::builder().kind(MultiPartKind::Related)
+    }
+
+    /// Creates encrypted multipart builder
+    ///
+    /// Shortcut for `MultiPart::builder().kind(MultiPartKind::Encrypted{ protocol })`
+    pub fn encrypted(protocol: String) -> MultiPartBuilder {
+        MultiPart::builder().kind(MultiPartKind::Encrypted { protocol })
+    }
+
+    /// Creates signed multipart builder
+    ///
+    /// Shortcut for `MultiPart::builder().kind(MultiPartKind::Signed{ protocol, micalg })`
+    pub fn signed(protocol: String, micalg: String) -> MultiPartBuilder {
+        MultiPart::builder().kind(MultiPartKind::Signed { protocol, micalg })
+    }
+
+    /// Add part to multipart
+    pub fn part(mut self, part: Part) -> Self {
+        self.parts.push(part);
+        self
+    }
+
+    /// Add single part to multipart
+    pub fn singlepart(mut self, part: SinglePart) -> Self {
+        self.parts.push(Part::Single(part));
+        self
+    }
+
+    /// Add multi part to multipart
+    pub fn multipart(mut self, part: MultiPart) -> Self {
+        self.parts.push(Part::Multi(part));
+        self
+    }
+
+    /// Get the boundary of multipart contents
+    pub fn boundary(&self) -> String {
+        let content_type = &self.headers.get::<ContentType>().unwrap().0;
+        content_type.get_param("boundary").unwrap().as_str().into()
+    }
+
+    /// Get the headers from the multipart
+    pub fn headers(&self) -> &Headers {
+        &self.headers
+    }
+
+    /// Get a mutable reference to the headers
+    pub fn headers_mut(&mut self) -> &mut Headers {
+        &mut self.headers
+    }
+
+    /// Get the parts from the multipart
+    pub fn parts(&self) -> &Parts {
+        &self.parts
+    }
+
+    /// Get a mutable reference to the parts
+    pub fn parts_mut(&mut self) -> &mut Parts {
+        &mut self.parts
+    }
+
+    /// Get message content formatted for SMTP
+    pub fn formatted(&self) -> Vec<u8> {
+        let mut out = Vec::new();
+        self.format(&mut out);
+        out
+    }
+}
+
+impl EmailFormat for MultiPart {
+    fn format(&self, out: &mut Vec<u8>) {
+        out.extend_from_slice(self.headers.to_string().as_bytes());
+        out.extend_from_slice(b"\r\n");
+
+        let boundary = self.boundary();
+
+        for part in &self.parts {
+            out.extend_from_slice(b"--");
+            out.extend_from_slice(boundary.as_bytes());
+            out.extend_from_slice(b"\r\n");
+            part.format(out);
+        }
+
+        out.extend_from_slice(b"--");
+        out.extend_from_slice(boundary.as_bytes());
+        out.extend_from_slice(b"--\r\n");
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::message::header;
+
+    #[test]
+    fn single_part_binary() {
+        let part = SinglePart::builder()
+            .header(header::ContentType(
+                "text/plain; charset=utf8".parse().unwrap(),
+            ))
+            .header(header::ContentTransferEncoding::Binary)
+            .body(String::from("Текст письма в уникоде"));
+
+        assert_eq!(
+            String::from_utf8(part.formatted()).unwrap(),
+            concat!(
+                "Content-Type: text/plain; charset=utf8\r\n",
+                "Content-Transfer-Encoding: binary\r\n",
+                "\r\n",
+                "Текст письма в уникоде\r\n"
+            )
+        );
+    }
+
+    #[test]
+    fn single_part_quoted_printable() {
+        let part = SinglePart::builder()
+            .header(header::ContentType(
+                "text/plain; charset=utf8".parse().unwrap(),
+            ))
+            .header(header::ContentTransferEncoding::QuotedPrintable)
+            .body(String::from("Текст письма в уникоде"));
+
+        assert_eq!(
+            String::from_utf8(part.formatted()).unwrap(),
+            concat!(
+                "Content-Type: text/plain; charset=utf8\r\n",
+                "Content-Transfer-Encoding: quoted-printable\r\n",
+                "\r\n",
+                "=D0=A2=D0=B5=D0=BA=D1=81=D1=82 =D0=BF=D0=B8=D1=81=D1=8C=D0=BC=D0=B0 =D0=B2 =\r\n",
+                "=D1=83=D0=BD=D0=B8=D0=BA=D0=BE=D0=B4=D0=B5\r\n"
+            )
+        );
+    }
+
+    #[test]
+    fn single_part_base64() {
+        let part = SinglePart::builder()
+            .header(header::ContentType(
+                "text/plain; charset=utf8".parse().unwrap(),
+            ))
+            .header(header::ContentTransferEncoding::Base64)
+            .body(String::from("Текст письма в уникоде"));
+
+        assert_eq!(
+            String::from_utf8(part.formatted()).unwrap(),
+            concat!(
+                "Content-Type: text/plain; charset=utf8\r\n",
+                "Content-Transfer-Encoding: base64\r\n",
+                "\r\n",
+                "0KLQtdC60YHRgiDQv9C40YHRjNC80LAg0LIg0YPQvdC40LrQvtC00LU=\r\n"
+            )
+        );
+    }
+
+    #[test]
+    fn multi_part_mixed() {
+        let part = MultiPart::mixed()
+            .boundary("F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK")
+            .part(Part::Single(
+                SinglePart::builder()
+                    .header(header::ContentType(
+                        "text/plain; charset=utf8".parse().unwrap(),
+                    ))
+                    .header(header::ContentTransferEncoding::Binary)
+                    .body(String::from("Текст письма в уникоде")),
+            ))
+            .singlepart(
+                SinglePart::builder()
+                    .header(header::ContentType(
+                        "text/plain; charset=utf8".parse().unwrap(),
+                    ))
+                    .header(header::ContentDisposition {
+                        disposition: header::DispositionType::Attachment,
+                        parameters: vec![header::DispositionParam::Filename(
+                            header::Charset::Ext("utf-8".into()),
+                            None,
+                            "example.c".into(),
+                        )],
+                    })
+                    .header(header::ContentTransferEncoding::Binary)
+                    .body(String::from("int main() { return 0; }")),
+            );
+
+        assert_eq!(String::from_utf8(part.formatted()).unwrap(),
+                   concat!("Content-Type: multipart/mixed;",
+                           " boundary=\"F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\"\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: text/plain; charset=utf8\r\n",
+                           "Content-Transfer-Encoding: binary\r\n",
+                           "\r\n",
+                           "Текст письма в уникоде\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: text/plain; charset=utf8\r\n",
+                           "Content-Disposition: attachment; filename=\"example.c\"\r\n",
+                           "Content-Transfer-Encoding: binary\r\n",
+                           "\r\n",
+                           "int main() { return 0; }\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK--\r\n"));
+    }
+    #[test]
+    fn multi_part_encrypted() {
+        let part = MultiPart::encrypted("application/pgp-encrypted".to_owned())
+            .boundary("F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK")
+            .part(Part::Single(
+                SinglePart::builder()
+                    .header(header::ContentType(
+                        "application/pgp-encrypted".parse().unwrap(),
+                    ))
+                    .body(String::from("Version: 1")),
+            ))
+            .singlepart(
+                SinglePart::builder()
+                    .header(ContentType(
+                        "application/octet-stream; name=\"encrypted.asc\""
+                            .parse()
+                            .unwrap(),
+                    ))
+                    .header(header::ContentDisposition {
+                        disposition: header::DispositionType::Inline,
+                        parameters: vec![header::DispositionParam::Filename(
+                            header::Charset::Ext("utf-8".into()),
+                            None,
+                            "encrypted.asc".into(),
+                        )],
+                    })
+                    .body(String::from(concat!(
+                        "-----BEGIN PGP MESSAGE-----\r\n",
+                        "wV4D0dz5vDXklO8SAQdA5lGX1UU/eVQqDxNYdHa7tukoingHzqUB6wQssbMfHl8w\r\n",
+                        "...\r\n",
+                        "-----END PGP MESSAGE-----\r\n"
+                    ))),
+            );
+
+        assert_eq!(String::from_utf8(part.formatted()).unwrap(),
+                   concat!("Content-Type: multipart/encrypted;",
+                           " boundary=\"F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\";",
+                           " protocol=\"application/pgp-encrypted\"\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: application/pgp-encrypted\r\n",
+                           "Content-Transfer-Encoding: 7bit\r\n",
+                           "\r\n",
+                           "Version: 1\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: application/octet-stream; name=\"encrypted.asc\"\r\n",
+                           "Content-Disposition: inline; filename=\"encrypted.asc\"\r\n",
+                           "Content-Transfer-Encoding: 7bit\r\n",
+                           "\r\n",
+                           "-----BEGIN PGP MESSAGE-----\r\n",
+                           "wV4D0dz5vDXklO8SAQdA5lGX1UU/eVQqDxNYdHa7tukoingHzqUB6wQssbMfHl8w\r\n",
+                           "...\r\n",
+                           "-----END PGP MESSAGE-----\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK--\r\n"));
+    }
+    #[test]
+    fn multi_part_signed() {
+        let part = MultiPart::signed(
+            "application/pgp-signature".to_owned(),
+            "pgp-sha256".to_owned(),
+        )
+        .boundary("F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK")
+        .part(Part::Single(
+            SinglePart::builder()
+                .header(header::ContentType("text/plain".parse().unwrap()))
+                .body(String::from("Test email for signature")),
+        ))
+        .singlepart(
+            SinglePart::builder()
+                .header(ContentType(
+                    "application/pgp-signature; name=\"signature.asc\""
+                        .parse()
+                        .unwrap(),
+                ))
+                .header(header::ContentDisposition {
+                    disposition: header::DispositionType::Attachment,
+                    parameters: vec![header::DispositionParam::Filename(
+                        header::Charset::Ext("utf-8".into()),
+                        None,
+                        "signature.asc".into(),
+                    )],
+                })
+                .body(String::from(concat!(
+                    "-----BEGIN PGP SIGNATURE-----\r\n",
+                    "\r\n",
+                    "iHUEARYIAB0WIQTNsp3S/GbdE0KoiQ+IGQOscREZuQUCXyOzDAAKCRCIGQOscREZ\r\n",
+                    "udgDAQCv3FJ3QWW5bRaGZAa0Ug6vASFdkvDMKoRwcoFnHPthjQEAiQ8skkIyE2GE\r\n",
+                    "PoLpAXiKpT+NU8S8+8dfvwutnb4dSwM=\r\n",
+                    "=3FYZ\r\n",
+                    "-----END PGP SIGNATURE-----\r\n",
+                ))),
+        );
+
+        assert_eq!(String::from_utf8(part.formatted()).unwrap(),
+                   concat!("Content-Type: multipart/signed;",
+                           " boundary=\"F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\";",
+                           " protocol=\"application/pgp-signature\";",
+                           " micalg=\"pgp-sha256\"\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: text/plain\r\n",
+                           "Content-Transfer-Encoding: 7bit\r\n",
+                           "\r\n",
+                           "Test email for signature\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: application/pgp-signature; name=\"signature.asc\"\r\n",
+                           "Content-Disposition: attachment; filename=\"signature.asc\"\r\n",
+                           "Content-Transfer-Encoding: 7bit\r\n",
+                           "\r\n",
+                           "-----BEGIN PGP SIGNATURE-----\r\n",
+                            "\r\n",
+                            "iHUEARYIAB0WIQTNsp3S/GbdE0KoiQ+IGQOscREZuQUCXyOzDAAKCRCIGQOscREZ\r\n",
+                            "udgDAQCv3FJ3QWW5bRaGZAa0Ug6vASFdkvDMKoRwcoFnHPthjQEAiQ8skkIyE2GE\r\n",
+                            "PoLpAXiKpT+NU8S8+8dfvwutnb4dSwM=\r\n",
+                            "=3FYZ\r\n",
+                            "-----END PGP SIGNATURE-----\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK--\r\n"));
+    }
+
+    #[test]
+    fn multi_part_alternative() {
+        let part = MultiPart::alternative()
+            .boundary("F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK")
+            .part(Part::Single(SinglePart::builder()
+                             .header(header::ContentType("text/plain; charset=utf8".parse().unwrap()))
+                             .header(header::ContentTransferEncoding::Binary)
+                             .body(String::from("Текст письма в уникоде"))))
+            .singlepart(SinglePart::builder()
+                             .header(header::ContentType("text/html; charset=utf8".parse().unwrap()))
+                             .header(header::ContentTransferEncoding::Binary)
+                             .body(String::from("<p>Текст <em>письма</em> в <a href=\"https://ru.wikipedia.org/wiki/Юникод\">уникоде</a><p>")));
+
+        assert_eq!(String::from_utf8(part.formatted()).unwrap(),
+                   concat!("Content-Type: multipart/alternative;",
+                           " boundary=\"F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\"\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: text/plain; charset=utf8\r\n",
+                           "Content-Transfer-Encoding: binary\r\n",
+                           "\r\n",
+                           "Текст письма в уникоде\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: text/html; charset=utf8\r\n",
+                           "Content-Transfer-Encoding: binary\r\n",
+                           "\r\n",
+                           "<p>Текст <em>письма</em> в <a href=\"https://ru.wikipedia.org/wiki/Юникод\">уникоде</a><p>\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK--\r\n"));
+    }
+
+    #[test]
+    fn multi_part_mixed_related() {
+        let part = MultiPart::mixed()
+            .boundary("F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK")
+            .multipart(MultiPart::related()
+                            .boundary("E912L4JH3loAAAAAFu/33Gx7PEoTMmhGaxG3FlbVMQHctj96q4nHvBM+7DTtXo/im8gh")
+                            .singlepart(SinglePart::builder()
+                                             .header(header::ContentType("text/html; charset=utf8".parse().unwrap()))
+                                             .header(header::ContentTransferEncoding::Binary)
+                                             .body(String::from("<p>Текст <em>письма</em> в <a href=\"https://ru.wikipedia.org/wiki/Юникод\">уникоде</a><p>")))
+                            .singlepart(SinglePart::builder()
+                                             .header(header::ContentType("image/png".parse().unwrap()))
+                                             .header(header::ContentLocation("/image.png".into()))
+                                             .header(header::ContentTransferEncoding::Base64)
+                                             .body(String::from("1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"))))
+            .singlepart(SinglePart::builder()
+                             .header(header::ContentType("text/plain; charset=utf8".parse().unwrap()))
+                             .header(header::ContentDisposition {
+                                 disposition: header::DispositionType::Attachment,
+                                 parameters: vec![header::DispositionParam::Filename(header::Charset::Ext("utf-8".into()), None, "example.c".into())]
+                             })
+                             .header(header::ContentTransferEncoding::Binary)
+                             .body(String::from("int main() { return 0; }")));
+
+        assert_eq!(String::from_utf8(part.formatted()).unwrap(),
+                   concat!("Content-Type: multipart/mixed;",
+                           " boundary=\"F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\"\r\n",
+                           "\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: multipart/related;",
+                           " boundary=\"E912L4JH3loAAAAAFu/33Gx7PEoTMmhGaxG3FlbVMQHctj96q4nHvBM+7DTtXo/im8gh\"\r\n",
+                           "\r\n",
+                           "--E912L4JH3loAAAAAFu/33Gx7PEoTMmhGaxG3FlbVMQHctj96q4nHvBM+7DTtXo/im8gh\r\n",
+                           "Content-Type: text/html; charset=utf8\r\n",
+                           "Content-Transfer-Encoding: binary\r\n",
+                           "\r\n",
+                           "<p>Текст <em>письма</em> в <a href=\"https://ru.wikipedia.org/wiki/Юникод\">уникоде</a><p>\r\n",
+                           "--E912L4JH3loAAAAAFu/33Gx7PEoTMmhGaxG3FlbVMQHctj96q4nHvBM+7DTtXo/im8gh\r\n",
+                           "Content-Type: image/png\r\n",
+                           "Content-Location: /image.png\r\n",
+                           "Content-Transfer-Encoding: base64\r\n",
+                           "\r\n",
+                           "MTIzNDU2Nzg5MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIzNDU2Nzg5MDEyMzQ1Njc4OTAxMjM0NTY3\r\n",
+                           "ODkwMTIzNDU2Nzg5MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIzNDU2Nzg5MDEyMzQ1Njc4OTAxMjM0\r\n",
+                           "NTY3ODkwMTIzNDU2Nzg5MA==\r\n",
+                           "--E912L4JH3loAAAAAFu/33Gx7PEoTMmhGaxG3FlbVMQHctj96q4nHvBM+7DTtXo/im8gh--\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK\r\n",
+                           "Content-Type: text/plain; charset=utf8\r\n",
+                           "Content-Disposition: attachment; filename=\"example.c\"\r\n",
+                           "Content-Transfer-Encoding: binary\r\n",
+                           "\r\n",
+                           "int main() { return 0; }\r\n",
+                           "--F2mTKN843loAAAAA8porEdAjCKhArPxGeahYoZYSftse1GT/84tup+O0bs8eueVuAlMK--\r\n"));
+    }
+
+    #[test]
+    fn test_make_boundary() {
+        let mut boundaries = std::collections::HashSet::with_capacity(10);
+        for _ in 0..1000 {
+            boundaries.insert(make_boundary());
+        }
+
+        // Ensure there are no duplicates
+        assert_eq!(1000, boundaries.len());
+
+        // Ensure correct length
+        for boundary in boundaries {
+            assert_eq!(40, boundary.len());
+        }
+    }
+}

src/message/mod.rs

@@ -0,0 +1,661 @@
+//! Provides a strongly typed way to build emails
+//!
+//! ## Usage
+//!
+//! This section demonstrates how to build messages.
+//!
+//! <!--
+//! style for <details><summary>Blablabla</summary> Lots of stuff</details>
+//! borrowed from https://docs.rs/time/0.2.23/src/time/lib.rs.html#49-54
+//! -->
+//! <style>
+//! summary, details:not([open]) { cursor: pointer; }
+//! summary { display: list-item; }
+//! summary::marker { content: '▶ '; }
+//! details[open] summary::marker { content: '▼ '; }
+//! </style>
+//!
+//!
+//! ### Plain body
+//!
+//! The easiest way of creating a message, which uses a plain text body.
+//!
+//! ```rust
+//! use lettre::message::Message;
+//!
+//! # use std::error::Error;
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! let m = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! Which produces:
+//! <details>
+//! <summary>Click to expand</summary>
+//!
+//! ```sh
+//! From: NoBody <nobody@domain.tld>
+//! Reply-To: Yuin <yuin@domain.tld>
+//! To: Hei <hei@domain.tld>
+//! Subject: Happy new year
+//! Date: Sat, 12 Dec 2020 16:33:19 GMT
+//! Content-Transfer-Encoding: 7bit
+//!
+//! Be happy!
+//! ```
+//! </details>
+//! <br />
+//!
+//! The unicode header data is encoded using _UTF8-Base64_ encoding, when necessary.
+//!
+//! The `Content-Transfer-Encoding` is chosen based on the best encoding
+//! available for the given body, between `7bit`, `quoted-printable` and `base64`.
+//!
+//! ### Plain and HTML body
+//!
+//! Uses a MIME body to include both plain text and HTML versions of the body.
+//!
+//! ```rust
+//! # use std::error::Error;
+//! use lettre::message::{header, Message, MultiPart, Part, SinglePart};
+//!
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! let m = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .multipart(
+//!         MultiPart::alternative()
+//!             .singlepart(
+//!                 SinglePart::builder()
+//!                     .header(header::ContentType("text/plain; charset=utf8".parse()?))
+//!                     .body(String::from("Hello, world! :)")),
+//!             )
+//!             .singlepart(
+//!                 SinglePart::builder()
+//!                     .header(header::ContentType("text/html; charset=utf8".parse()?))
+//!                     .body(String::from(
+//!                         "<p><b>Hello</b>, <i>world</i>! <img src=\"cid:123\"></p>",
+//!                     )),
+//!             ),
+//!     )?;
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! Which produces:
+//! <details>
+//! <summary>Click to expand</summary>
+//!
+//! ```sh
+//! From: NoBody <nobody@domain.tld>
+//! Reply-To: Yuin <yuin@domain.tld>
+//! To: Hei <hei@domain.tld>
+//! Subject: Happy new year
+//! MIME-Version: 1.0
+//! Date: Sat, 12 Dec 2020 16:33:19 GMT
+//! Content-Type: multipart/alternative; boundary="0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1"
+//!
+//! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1
+//! Content-Type: text/plain; charset=utf8
+//! Content-Transfer-Encoding: 7bit
+//!
+//! Hello, world! :)
+//! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1
+//! Content-Type: text/html; charset=utf8
+//! Content-Transfer-Encoding: 7bit
+//!
+//! <p><b>Hello</b>, <i>world</i>! <img src="cid:123"></p>
+//! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1--
+//! ```
+//! </details>
+//!
+//! ### Complex MIME body
+//!
+//! This example shows how to include both plain and HTML versions of the body,
+//! attachments and inlined images.
+//!
+//! ```rust
+//! # use std::error::Error;
+//! use lettre::message::{header, Body, Message, MultiPart, Part, SinglePart};
+//! use std::fs;
+//!
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! let image = fs::read("docs/lettre.png")?;
+//! // this image_body can be cloned and reused between emails.
+//! // since `Body` holds a pre-encoded body, reusing it means avoiding having
+//! // to re-encode the same body for every email (this clearly only applies
+//! // when sending multiple emails with the same attachment).
+//! let image_body = Body::new(image);
+//!
+//! let m = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .multipart(
+//!         MultiPart::mixed()
+//!             .multipart(
+//!                 MultiPart::alternative()
+//!                     .singlepart(
+//!                         SinglePart::builder()
+//!                             .header(header::ContentType("text/plain; charset=utf8".parse()?))
+//!                             .body(String::from("Hello, world! :)")),
+//!                     )
+//!                     .multipart(
+//!                         MultiPart::related()
+//!                             .singlepart(
+//!                                 SinglePart::builder()
+//!                                     .header(header::ContentType(
+//!                                         "text/html; charset=utf8".parse()?,
+//!                                     ))
+//!                                     .body(String::from(
+//!                                         "<p><b>Hello</b>, <i>world</i>! <img src=cid:123></p>",
+//!                                     )),
+//!                             )
+//!                             .singlepart(
+//!                                 SinglePart::builder()
+//!                                     .header(header::ContentType("image/png".parse()?))
+//!                                     .header(header::ContentDisposition {
+//!                                         disposition: header::DispositionType::Inline,
+//!                                         parameters: vec![],
+//!                                     })
+//!                                     .header(header::ContentId("<123>".into()))
+//!                                     .body(image_body),
+//!                             ),
+//!                     ),
+//!             )
+//!             .singlepart(
+//!                 SinglePart::builder()
+//!                     .header(header::ContentType("text/plain; charset=utf8".parse()?))
+//!                     .header(header::ContentDisposition {
+//!                         disposition: header::DispositionType::Attachment,
+//!                         parameters: vec![header::DispositionParam::Filename(
+//!                             header::Charset::Ext("utf-8".into()),
+//!                             None,
+//!                             "example.rs".as_bytes().into(),
+//!                         )],
+//!                     })
+//!                     .body(String::from("fn main() { println!(\"Hello, World!\") }")),
+//!             ),
+//!     )?;
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! Which produces:
+//! <details>
+//! <summary>Click to expand</summary>
+//!
+//! ```sh
+//! From: NoBody <nobody@domain.tld>
+//! Reply-To: Yuin <yuin@domain.tld>
+//! To: Hei <hei@domain.tld>
+//! Subject: Happy new year
+//! MIME-Version: 1.0
+//! Date: Sat, 12 Dec 2020 16:30:45 GMT
+//! Content-Type: multipart/mixed; boundary="0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1"
+//!
+//! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1
+//! Content-Type: multipart/alternative; boundary="EyXdAZIgZuyUjAounq4Aj44a6MpJfqCKhm6pE1zk"
+//!
+//! --EyXdAZIgZuyUjAounq4Aj44a6MpJfqCKhm6pE1zk
+//! Content-Type: text/plain; charset=utf8
+//! Content-Transfer-Encoding: 7bit
+//!
+//! Hello, world! :)
+//! --EyXdAZIgZuyUjAounq4Aj44a6MpJfqCKhm6pE1zk
+//! Content-Type: multipart/related; boundary="eM5Z18WZVOQsqi5GQ71XGAXk6NNvHUA1Xv1FWrXr"
+//!
+//! --eM5Z18WZVOQsqi5GQ71XGAXk6NNvHUA1Xv1FWrXr
+//! Content-Type: text/html; charset=utf8
+//! Content-Transfer-Encoding: 7bit
+//!
+//! <p><b>Hello</b>, <i>world</i>! <img src=cid:123></p>
+//! --eM5Z18WZVOQsqi5GQ71XGAXk6NNvHUA1Xv1FWrXr
+//! Content-Type: image/png
+//! Content-Disposition: inline
+//! Content-ID: <123>
+//! Content-Transfer-Encoding: base64
+//!
+//! PHNtaWxlLXJhdy1pbWFnZS1kYXRhPg==
+//! --eM5Z18WZVOQsqi5GQ71XGAXk6NNvHUA1Xv1FWrXr--
+//! --EyXdAZIgZuyUjAounq4Aj44a6MpJfqCKhm6pE1zk--
+//! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1
+//! Content-Type: text/plain; charset=utf8
+//! Content-Disposition: attachment; filename="example.rs"
+//! Content-Transfer-Encoding: 7bit
+//!
+//! fn main() { println!("Hello, World!") }
+//! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1--
+//! ```
+//! </details>
+
+pub use body::{Body, IntoBody, MaybeString};
+pub use mailbox::*;
+pub use mimebody::*;
+
+pub use mime;
+
+mod body;
+pub mod header;
+mod mailbox;
+mod mimebody;
+mod utf8_b;
+
+use std::{convert::TryFrom, time::SystemTime};
+
+use uuid::Uuid;
+
+use crate::{
+    address::Envelope,
+    message::header::{ContentTransferEncoding, EmailDate, Header, Headers, MailboxesHeader},
+    Error as EmailError,
+};
+
+const DEFAULT_MESSAGE_ID_DOMAIN: &str = "localhost";
+
+/// Something that can be formatted as an email message
+trait EmailFormat {
+    // Use a writer?
+    fn format(&self, out: &mut Vec<u8>);
+}
+
+/// A builder for messages
+#[derive(Debug, Clone)]
+pub struct MessageBuilder {
+    headers: Headers,
+    envelope: Option<Envelope>,
+}
+
+impl MessageBuilder {
+    /// Creates a new default message builder
+    pub fn new() -> Self {
+        Self {
+            headers: Headers::new(),
+            envelope: None,
+        }
+    }
+
+    /// Set custom header to message
+    pub fn header<H: Header>(mut self, header: H) -> Self {
+        self.headers.set(header);
+        self
+    }
+
+    /// Add mailbox to header
+    pub fn mailbox<H: Header + MailboxesHeader>(mut self, header: H) -> Self {
+        if self.headers.has::<H>() {
+            self.headers.get_mut::<H>().unwrap().join_mailboxes(header);
+            self
+        } else {
+            self.header(header)
+        }
+    }
+
+    /// Add `Date` header to message
+    ///
+    /// Shortcut for `self.header(header::Date(date))`.
+    pub fn date(self, date: EmailDate) -> Self {
+        self.header(header::Date(date))
+    }
+
+    /// Set `Date` header using current date/time
+    ///
+    /// Shortcut for `self.date(SystemTime::now())`.
+    pub fn date_now(self) -> Self {
+        self.date(SystemTime::now().into())
+    }
+
+    /// Set `Subject` header to message
+    ///
+    /// Shortcut for `self.header(header::Subject(subject.into()))`.
+    pub fn subject<S: Into<String>>(self, subject: S) -> Self {
+        self.header(header::Subject(subject.into()))
+    }
+
+    /// Set `Mime-Version` header to 1.0
+    ///
+    /// Shortcut for `self.header(header::MIME_VERSION_1_0)`.
+    ///
+    /// Not exposed as it is set by body methods
+    fn mime_1_0(self) -> Self {
+        self.header(header::MIME_VERSION_1_0)
+    }
+
+    /// Set `Sender` header. Should be used when providing several `From` mailboxes.
+    ///
+    /// Defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.2).
+    ///
+    /// Shortcut for `self.header(header::Sender(mbox))`.
+    pub fn sender(self, mbox: Mailbox) -> Self {
+        self.header(header::Sender(mbox))
+    }
+
+    /// Set or add mailbox to `From` header
+    ///
+    /// Defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.2).
+    ///
+    /// Shortcut for `self.mailbox(header::From(mbox))`.
+    pub fn from(self, mbox: Mailbox) -> Self {
+        self.mailbox(header::From(mbox.into()))
+    }
+
+    /// Set or add mailbox to `ReplyTo` header
+    ///
+    /// Defined in [RFC5322](https://tools.ietf.org/html/rfc5322#section-3.6.2).
+    ///
+    /// Shortcut for `self.mailbox(header::ReplyTo(mbox))`.
+    pub fn reply_to(self, mbox: Mailbox) -> Self {
+        self.mailbox(header::ReplyTo(mbox.into()))
+    }
+
+    /// Set or add mailbox to `To` header
+    ///
+    /// Shortcut for `self.mailbox(header::To(mbox))`.
+    pub fn to(self, mbox: Mailbox) -> Self {
+        self.mailbox(header::To(mbox.into()))
+    }
+
+    /// Set or add mailbox to `Cc` header
+    ///
+    /// Shortcut for `self.mailbox(header::Cc(mbox))`.
+    pub fn cc(self, mbox: Mailbox) -> Self {
+        self.mailbox(header::Cc(mbox.into()))
+    }
+
+    /// Set or add mailbox to `Bcc` header
+    ///
+    /// Shortcut for `self.mailbox(header::Bcc(mbox))`.
+    pub fn bcc(self, mbox: Mailbox) -> Self {
+        self.mailbox(header::Bcc(mbox.into()))
+    }
+
+    /// Set or add message id to [`In-Reply-To`
+    /// header](https://tools.ietf.org/html/rfc5322#section-3.6.4)
+    pub fn in_reply_to(self, id: String) -> Self {
+        self.header(header::InReplyTo(id))
+    }
+
+    /// Set or add message id to [`References`
+    /// header](https://tools.ietf.org/html/rfc5322#section-3.6.4)
+    pub fn references(self, id: String) -> Self {
+        self.header(header::References(id))
+    }
+
+    /// Set [Message-Id
+    /// header](https://tools.ietf.org/html/rfc5322#section-3.6.4)
+    ///
+    /// Should generally be inserted by the mail relay.
+    ///
+    /// If `None` is provided, an id will be generated in the
+    /// `<UUID@HOSTNAME>`.
+    pub fn message_id(self, id: Option<String>) -> Self {
+        match id {
+            Some(i) => self.header(header::MessageId(i)),
+            None => {
+                #[cfg(feature = "hostname")]
+                let hostname = hostname::get()
+                    .map_err(|_| ())
+                    .and_then(|s| s.into_string().map_err(|_| ()))
+                    .unwrap_or_else(|_| DEFAULT_MESSAGE_ID_DOMAIN.to_string());
+                #[cfg(not(feature = "hostname"))]
+                let hostname = DEFAULT_MESSAGE_ID_DOMAIN.to_string();
+
+                self.header(header::MessageId(
+                    // https://tools.ietf.org/html/rfc5322#section-3.6.4
+                    format!("<{}@{}>", Uuid::new_v4(), hostname),
+                ))
+            }
+        }
+    }
+
+    /// Set [User-Agent
+    /// header](https://tools.ietf.org/html/draft-melnikov-email-user-agent-004)
+    pub fn user_agent(self, id: String) -> Self {
+        self.header(header::UserAgent(id))
+    }
+
+    /// Force specific envelope (by default it is derived from headers)
+    pub fn envelope(mut self, envelope: Envelope) -> Self {
+        self.envelope = Some(envelope);
+        self
+    }
+
+    // TODO: High-level methods for attachments and embedded files
+
+    /// Create message from body
+    fn build(self, body: MessageBody) -> Result<Message, EmailError> {
+        // Check for missing required headers
+        // https://tools.ietf.org/html/rfc5322#section-3.6
+
+        // Insert Date if missing
+        let res = if self.headers.get::<header::Date>().is_none() {
+            self.date_now()
+        } else {
+            self
+        };
+
+        // Fail is missing correct originator (Sender or From)
+        match res.headers.get::<header::From>() {
+            Some(header::From(f)) => {
+                let from: Vec<Mailbox> = f.clone().into();
+                if from.len() > 1 && res.headers.get::<header::Sender>().is_none() {
+                    return Err(EmailError::TooManyFrom);
+                }
+            }
+            None => {
+                return Err(EmailError::MissingFrom);
+            }
+        }
+
+        let envelope = match res.envelope {
+            Some(e) => e,
+            None => Envelope::try_from(&res.headers)?,
+        };
+        Ok(Message {
+            headers: res.headers,
+            body,
+            envelope,
+        })
+    }
+
+    /// Create [`Message`] using a [`Vec<u8>`], [`String`], or [`Body`] body
+    ///
+    /// Automatically gets encoded with `7bit`, `quoted-printable` or `base64`
+    /// `Content-Transfer-Encoding`, based on the most efficient and valid encoding
+    /// for `body`.
+    pub fn body<T: IntoBody>(mut self, body: T) -> Result<Message, EmailError> {
+        let maybe_encoding = self.headers.get::<ContentTransferEncoding>().copied();
+        let body = body.into_body(maybe_encoding);
+
+        self.headers.set(body.encoding());
+        self.build(MessageBody::Raw(body.into_vec()))
+    }
+
+    /// Create message using mime body ([`MultiPart`][self::MultiPart])
+    pub fn multipart(self, part: MultiPart) -> Result<Message, EmailError> {
+        self.mime_1_0().build(MessageBody::Mime(Part::Multi(part)))
+    }
+
+    /// Create message using mime body ([`SinglePart`][self::SinglePart])
+    pub fn singlepart(self, part: SinglePart) -> Result<Message, EmailError> {
+        self.mime_1_0().build(MessageBody::Mime(Part::Single(part)))
+    }
+}
+
+/// Email message which can be formatted
+#[derive(Clone, Debug)]
+pub struct Message {
+    headers: Headers,
+    body: MessageBody,
+    envelope: Envelope,
+}
+
+#[derive(Clone, Debug)]
+enum MessageBody {
+    Mime(Part),
+    Raw(Vec<u8>),
+}
+
+impl Message {
+    /// Create a new message builder without headers
+    pub fn builder() -> MessageBuilder {
+        MessageBuilder::new()
+    }
+
+    /// Get the headers from the Message
+    pub fn headers(&self) -> &Headers {
+        &self.headers
+    }
+
+    /// Get `Message` envelope
+    pub fn envelope(&self) -> &Envelope {
+        &self.envelope
+    }
+
+    /// Get message content formatted for SMTP
+    pub fn formatted(&self) -> Vec<u8> {
+        let mut out = Vec::new();
+        self.format(&mut out);
+        out
+    }
+}
+
+impl EmailFormat for Message {
+    fn format(&self, out: &mut Vec<u8>) {
+        out.extend_from_slice(self.headers.to_string().as_bytes());
+
+        match &self.body {
+            MessageBody::Mime(p) => p.format(out),
+            MessageBody::Raw(r) => {
+                out.extend_from_slice(b"\r\n");
+                out.extend_from_slice(&r)
+            }
+        }
+    }
+}
+
+impl Default for MessageBuilder {
+    fn default() -> Self {
+        MessageBuilder::new()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::message::{header, mailbox::Mailbox, Message, MultiPart, SinglePart};
+
+    #[test]
+    fn email_missing_originator() {
+        assert!(Message::builder()
+            .body(String::from("Happy new year!"))
+            .is_err());
+    }
+
+    #[test]
+    fn email_miminal_message() {
+        assert!(Message::builder()
+            .from("NoBody <nobody@domain.tld>".parse().unwrap())
+            .to("NoBody <nobody@domain.tld>".parse().unwrap())
+            .body(String::from("Happy new year!"))
+            .is_ok());
+    }
+
+    #[test]
+    fn email_missing_sender() {
+        assert!(Message::builder()
+            .from("NoBody <nobody@domain.tld>".parse().unwrap())
+            .from("AnyBody <anybody@domain.tld>".parse().unwrap())
+            .body(String::from("Happy new year!"))
+            .is_err());
+    }
+
+    #[test]
+    fn email_message() {
+        let date = "Tue, 15 Nov 1994 08:12:31 GMT".parse().unwrap();
+
+        let email = Message::builder()
+            .date(date)
+            .header(header::From(
+                vec![Mailbox::new(
+                    Some("Каи".into()),
+                    "kayo@example.com".parse().unwrap(),
+                )]
+                .into(),
+            ))
+            .header(header::To(
+                vec!["Pony O.P. <pony@domain.tld>".parse().unwrap()].into(),
+            ))
+            .header(header::Subject("яңа ел белән!".into()))
+            .body(String::from("Happy new year!"))
+            .unwrap();
+
+        assert_eq!(
+            String::from_utf8(email.formatted()).unwrap(),
+            concat!(
+                "Date: Tue, 15 Nov 1994 08:12:31 GMT\r\n",
+                "From: =?utf-8?b?0JrQsNC4?= <kayo@example.com>\r\n",
+                "To: Pony O.P. <pony@domain.tld>\r\n",
+                "Subject: =?utf-8?b?0Y/So9CwINC10Lsg0LHQtdC705nQvSE=?=\r\n",
+                "Content-Transfer-Encoding: 7bit\r\n",
+                "\r\n",
+                "Happy new year!"
+            )
+        );
+    }
+
+    #[test]
+    fn email_with_png() {
+        let date = "Tue, 15 Nov 1994 08:12:31 GMT".parse().unwrap();
+        let img = std::fs::read("./docs/lettre.png").unwrap();
+        let m = Message::builder()
+            .date(date)
+            .from("NoBody <nobody@domain.tld>".parse().unwrap())
+            .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+            .to("Hei <hei@domain.tld>".parse().unwrap())
+            .subject("Happy new year")
+            .multipart(
+                MultiPart::related()
+                    .singlepart(
+                        SinglePart::builder()
+                            .header(header::ContentType(
+                                "text/html; charset=utf8".parse().unwrap(),
+                            ))
+                            .body(String::from(
+                                "<p><b>Hello</b>, <i>world</i>! <img src=cid:123></p>",
+                            )),
+                    )
+                    .singlepart(
+                        SinglePart::builder()
+                            .header(header::ContentType("image/png".parse().unwrap()))
+                            .header(header::ContentDisposition {
+                                disposition: header::DispositionType::Inline,
+                                parameters: vec![],
+                            })
+                            .header(header::ContentId("<123>".into()))
+                            .body(img),
+                    ),
+            )
+            .unwrap();
+
+        let output = String::from_utf8(m.formatted()).unwrap();
+        let file_expected = std::fs::read("./testdata/email_with_png.eml").unwrap();
+        let expected = String::from_utf8(file_expected).unwrap();
+
+        for (i, line) in output.lines().zip(expected.lines()).enumerate() {
+            if i == 6 || i == 8 || i == 13 || i == 232 {
+                continue;
+            }
+
+            assert_eq!(line.0, line.1)
+        }
+    }
+}

src/message/utf8_b.rs

@@ -0,0 +1,60 @@
+// https://tools.ietf.org/html/rfc1522
+
+fn allowed_char(c: char) -> bool {
+    c >= 1 as char && c <= 9 as char
+        || c == 11 as char
+        || c == 12 as char
+        || c >= 14 as char && c <= 127 as char
+}
+
+pub fn encode(s: &str) -> String {
+    if s.chars().all(allowed_char) {
+        s.into()
+    } else {
+        format!("=?utf-8?b?{}?=", base64::encode(s))
+    }
+}
+
+pub fn decode(s: &str) -> Option<String> {
+    s.strip_prefix("=?utf-8?b?")
+        .and_then(|stripped| stripped.strip_suffix("?="))
+        .map_or_else(
+            || Some(s.into()),
+            |stripped| {
+                let decoded = base64::decode(stripped).ok()?;
+                let decoded = String::from_utf8(decoded).ok()?;
+                Some(decoded)
+            },
+        )
+}
+
+#[cfg(test)]
+mod test {
+    use super::{decode, encode};
+
+    #[test]
+    fn encode_ascii() {
+        assert_eq!(&encode("Kayo. ?"), "Kayo. ?");
+    }
+
+    #[test]
+    fn decode_ascii() {
+        assert_eq!(decode("Kayo. ?"), Some("Kayo. ?".into()));
+    }
+
+    #[test]
+    fn encode_utf8() {
+        assert_eq!(
+            &encode("Привет, мир!"),
+            "=?utf-8?b?0J/RgNC40LLQtdGCLCDQvNC40YAh?="
+        );
+    }
+
+    #[test]
+    fn decode_utf8() {
+        assert_eq!(
+            decode("=?utf-8?b?0J/RgNC40LLQtdGCLCDQvNC40YAh?="),
+            Some("Привет, мир!".into())
+        );
+    }
+}

src/transport/file/error.rs

@@ -0,0 +1,61 @@
+//! Error and result type for file transport
+
+use self::Error::*;
+use std::{
+    error::Error as StdError,
+    fmt::{self, Display, Formatter},
+    io,
+};
+
+/// An enum of all error kinds.
+#[derive(Debug)]
+pub enum Error {
+    /// Internal client error
+    Client(&'static str),
+    /// IO error
+    Io(io::Error),
+    /// JSON error
+    #[cfg(feature = "file-transport-envelope")]
+    Json(serde_json::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), fmt::Error> {
+        match *self {
+            Client(err) => fmt.write_str(err),
+            Io(ref err) => err.fmt(fmt),
+            #[cfg(feature = "file-transport-envelope")]
+            Json(ref err) => err.fmt(fmt),
+        }
+    }
+}
+
+impl StdError for Error {
+    fn source(&self) -> Option<&(dyn StdError + 'static)> {
+        match *self {
+            Io(ref err) => Some(&*err),
+            #[cfg(feature = "file-transport-envelope")]
+            Json(ref err) => Some(&*err),
+            _ => None,
+        }
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(err: io::Error) -> Error {
+        Error::Io(err)
+    }
+}
+
+#[cfg(feature = "file-transport-envelope")]
+impl From<serde_json::Error> for Error {
+    fn from(err: serde_json::Error) -> Error {
+        Error::Json(err)
+    }
+}
+
+impl From<&'static str> for Error {
+    fn from(string: &'static str) -> Error {
+        Error::Client(string)
+    }
+}

src/transport/file/mod.rs

@@ -0,0 +1,314 @@
+//! The file transport writes the emails to the given directory. The name of the file will be
+//! `message_id.eml`.
+//! It can be useful for testing purposes, or if you want to keep track of sent messages.
+//!
+//! ## Sync example
+//!
+//! ```rust
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "file-transport", feature = "builder"))]
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! use lettre::{FileTransport, Message, Transport};
+//! use std::env::temp_dir;
+//!
+//! // Write to the local temp directory
+//! let sender = FileTransport::new(temp_dir());
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let result = sender.send(&email);
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//!
+//! # #[cfg(not(all(feature = "file-transport", feature = "builder")))]
+//! # fn main() {}
+//! ```
+//!
+//! ## Sync example with envelope
+//!
+//! It is possible to also write the envelope content in a separate JSON file
+//! by using the `with_envelope` builder. The JSON file will be written in the
+//! target directory with same name and a `json` extension.
+//!
+//! ```rust
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "file-transport-envelope", feature = "builder"))]
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! use lettre::{FileTransport, Message, Transport};
+//! use std::env::temp_dir;
+//!
+//! // Write to the local temp directory
+//! let sender = FileTransport::with_envelope(temp_dir());
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let result = sender.send(&email);
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//!
+//! # #[cfg(not(all(feature = "file-transport-envelope", feature = "builder")))]
+//! # fn main() {}
+//! ```
+//!
+//! ## Async tokio 1.x
+//!
+//! ```rust,no_run
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "tokio1", feature = "file-transport", feature = "builder"))]
+//! # async fn run() -> Result<(), Box<dyn Error>> {
+//! use std::env::temp_dir;
+//! use lettre::{AsyncTransport, Tokio1Executor, Message, AsyncFileTransport};
+//!
+//! // Write to the local temp directory
+//! let sender = AsyncFileTransport::<Tokio1Executor>::new(temp_dir());
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let result = sender.send(email).await;
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! ## Async async-std 1.x
+//!
+//! ```rust,no_run
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "async-std1", feature = "file-transport", feature = "builder"))]
+//! # async fn run() -> Result<(), Box<dyn Error>> {
+//! use std::env::temp_dir;
+//! use lettre::{AsyncTransport, AsyncStd1Executor, Message, AsyncFileTransport};
+//!
+//! // Write to the local temp directory
+//! let sender = AsyncFileTransport::<AsyncStd1Executor>::new(temp_dir());
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let result = sender.send(email).await;
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! ---
+//!
+//! Example email content result
+//!
+//! ```eml
+//! From: NoBody <nobody@domain.tld>
+//! Reply-To: Yuin <yuin@domain.tld>
+//! To: Hei <hei@domain.tld>
+//! Subject: Happy new year
+//! Date: Tue, 18 Aug 2020 22:50:17 GMT
+//!
+//! Be happy!
+//! ```
+//!
+//! Example envelope result
+//!
+//! ```json
+//! {"forward_path":["hei@domain.tld"],"reverse_path":"nobody@domain.tld"}
+//! ```
+
+pub use self::error::Error;
+use crate::{address::Envelope, Transport};
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use crate::{AsyncTransport, Executor};
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use async_trait::async_trait;
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use std::marker::PhantomData;
+use std::{
+    path::{Path, PathBuf},
+    str,
+};
+use uuid::Uuid;
+
+mod error;
+
+type Id = String;
+
+/// Writes the content and the envelope information to a file
+#[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct FileTransport {
+    path: PathBuf,
+    #[cfg(feature = "file-transport-envelope")]
+    save_envelope: bool,
+}
+
+#[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+pub struct AsyncFileTransport<E: Executor> {
+    inner: FileTransport,
+    marker_: PhantomData<E>,
+}
+
+impl FileTransport {
+    /// Creates a new transport to the given directory
+    ///
+    /// Writes the email content in eml format.
+    pub fn new<P: AsRef<Path>>(path: P) -> FileTransport {
+        FileTransport {
+            path: PathBuf::from(path.as_ref()),
+            #[cfg(feature = "file-transport-envelope")]
+            save_envelope: false,
+        }
+    }
+
+    /// Creates a new transport to the given directory
+    ///
+    /// Writes the email content in eml format and the envelope
+    /// in json format.
+    #[cfg(feature = "file-transport-envelope")]
+    pub fn with_envelope<P: AsRef<Path>>(path: P) -> FileTransport {
+        FileTransport {
+            path: PathBuf::from(path.as_ref()),
+            #[cfg(feature = "file-transport-envelope")]
+            save_envelope: true,
+        }
+    }
+
+    /// Read a message that was written using the file transport.
+    ///
+    /// Reads the envelope and the raw message content.
+    #[cfg(feature = "file-transport-envelope")]
+    pub fn read(&self, email_id: &str) -> Result<(Envelope, Vec<u8>), Error> {
+        use std::fs;
+
+        let eml_file = self.path.join(format!("{}.eml", email_id));
+        let eml = fs::read(eml_file)?;
+
+        let json_file = self.path.join(format!("{}.json", email_id));
+        let json = fs::read(&json_file)?;
+        let envelope = serde_json::from_slice(&json)?;
+
+        Ok((envelope, eml))
+    }
+
+    fn path(&self, email_id: &Uuid, extension: &str) -> PathBuf {
+        self.path.join(format!("{}.{}", email_id, extension))
+    }
+}
+
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+impl<E> AsyncFileTransport<E>
+where
+    E: Executor,
+{
+    /// Creates a new transport to the given directory
+    ///
+    /// Writes the email content in eml format.
+    pub fn new<P: AsRef<Path>>(path: P) -> Self {
+        Self {
+            inner: FileTransport::new(path),
+            marker_: PhantomData,
+        }
+    }
+
+    /// Creates a new transport to the given directory
+    ///
+    /// Writes the email content in eml format and the envelope
+    /// in json format.
+    #[cfg(feature = "file-transport-envelope")]
+    pub fn with_envelope<P: AsRef<Path>>(path: P) -> Self {
+        Self {
+            inner: FileTransport::with_envelope(path),
+            marker_: PhantomData,
+        }
+    }
+
+    /// Read a message that was written using the file transport.
+    ///
+    /// Reads the envelope and the raw message content.
+    #[cfg(feature = "file-transport-envelope")]
+    pub async fn read(&self, email_id: &str) -> Result<(Envelope, Vec<u8>), Error> {
+        let eml_file = self.inner.path.join(format!("{}.eml", email_id));
+        let eml = E::fs_read(&eml_file).await?;
+
+        let json_file = self.inner.path.join(format!("{}.json", email_id));
+        let json = E::fs_read(&json_file).await?;
+        let envelope = serde_json::from_slice(&json)?;
+
+        Ok((envelope, eml))
+    }
+}
+
+impl Transport for FileTransport {
+    type Ok = Id;
+    type Error = Error;
+
+    fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        use std::fs;
+
+        let email_id = Uuid::new_v4();
+
+        let file = self.path(&email_id, "eml");
+        fs::write(file, email)?;
+
+        #[cfg(feature = "file-transport-envelope")]
+        {
+            if self.save_envelope {
+                let file = self.path(&email_id, "json");
+                fs::write(file, serde_json::to_string(&envelope)?)?;
+            }
+        }
+        // use envelope anyway
+        let _ = envelope;
+
+        Ok(email_id.to_string())
+    }
+}
+
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+#[async_trait]
+impl<E> AsyncTransport for AsyncFileTransport<E>
+where
+    E: Executor,
+{
+    type Ok = Id;
+    type Error = Error;
+
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        let email_id = Uuid::new_v4();
+
+        let file = self.inner.path(&email_id, "eml");
+        E::fs_write(&file, email).await?;
+
+        #[cfg(feature = "file-transport-envelope")]
+        {
+            if self.inner.save_envelope {
+                let file = self.inner.path(&email_id, "json");
+                let buf = serde_json::to_vec(&envelope)?;
+                E::fs_write(&file, &buf).await?;
+            }
+        }
+        // use envelope anyway
+        let _ = envelope;
+
+        Ok(email_id.to_string())
+    }
+}

src/transport/mod.rs

@@ -0,0 +1,92 @@
+//! ### Sending Messages
+//!
+//! This section explains how to manipulate emails you have created.
+//!
+//! This mailer contains several different transports for your emails. To be sendable, the
+//! emails have to implement `Email`, which is the case for emails created with `lettre::builder`.
+//!
+//! The following transports are available:
+//!
+//! * The `SmtpTransport` uses the SMTP protocol to send the message over the network. It is
+//!   the preferred way of sending emails.
+//! * The `SendmailTransport` uses the sendmail command to send messages. It is an alternative to
+//!   the SMTP transport.
+//! * The `FileTransport` creates a file containing the email content to be sent. It can be used
+//!   for debugging or if you want to keep all sent emails.
+//! * The `StubTransport` is useful for debugging, and only prints the content of the email in the
+//!   logs.
+
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use async_trait::async_trait;
+
+#[doc(hidden)]
+#[deprecated(note = "use lettre::AsyncStd1Transport")]
+#[cfg(feature = "async-std1")]
+pub use self::AsyncTransport as AsyncStd1Transport;
+#[doc(hidden)]
+#[deprecated(note = "use lettre::Tokio1Transport")]
+#[cfg(feature = "tokio1")]
+pub use self::AsyncTransport as Tokio1Transport;
+#[doc(hidden)]
+#[deprecated(note = "use lettre::Tokio02Transport")]
+#[cfg(feature = "tokio02")]
+pub use self::AsyncTransport as Tokio02Transport;
+
+use crate::Envelope;
+#[cfg(feature = "builder")]
+use crate::Message;
+
+#[cfg(feature = "file-transport")]
+#[cfg_attr(docsrs, doc(cfg(feature = "file-transport")))]
+pub mod file;
+#[cfg(feature = "sendmail-transport")]
+#[cfg_attr(docsrs, doc(cfg(feature = "sendmail-transport")))]
+pub mod sendmail;
+#[cfg(feature = "smtp-transport")]
+#[cfg_attr(docsrs, doc(cfg(feature = "smtp-transport")))]
+pub mod smtp;
+pub mod stub;
+
+/// Blocking Transport method for emails
+pub trait Transport {
+    /// Response produced by the Transport
+    type Ok;
+    /// Error produced by the Transport
+    type Error;
+
+    /// Sends the email
+    #[cfg(feature = "builder")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "builder")))]
+    fn send(&self, message: &Message) -> Result<Self::Ok, Self::Error> {
+        let raw = message.formatted();
+        self.send_raw(message.envelope(), &raw)
+    }
+
+    fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Async Transport method for emails
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1")))
+)]
+#[async_trait]
+pub trait AsyncTransport {
+    /// Response produced by the Transport
+    type Ok;
+    /// Error produced by the Transport
+    type Error;
+
+    /// Sends the email
+    #[cfg(feature = "builder")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "builder")))]
+    // TODO take &Message
+    async fn send(&self, message: Message) -> Result<Self::Ok, Self::Error> {
+        let raw = message.formatted();
+        let envelope = message.envelope();
+        self.send_raw(&envelope, &raw).await
+    }
+
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error>;
+}

src/transport/sendmail/error.rs

@@ -0,0 +1,52 @@
+//! Error and result type for sendmail transport
+
+use self::Error::*;
+use std::{
+    error::Error as StdError,
+    fmt::{self, Display, Formatter},
+    io,
+    string::FromUtf8Error,
+};
+
+/// An enum of all error kinds.
+#[derive(Debug)]
+pub enum Error {
+    /// Internal client error
+    Client(String),
+    /// Error parsing UTF8 in response
+    Utf8Parsing(FromUtf8Error),
+    /// IO error
+    Io(io::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), fmt::Error> {
+        match *self {
+            Client(ref err) => err.fmt(fmt),
+            Utf8Parsing(ref err) => err.fmt(fmt),
+            Io(ref err) => err.fmt(fmt),
+        }
+    }
+}
+
+impl StdError for Error {
+    fn source(&self) -> Option<&(dyn StdError + 'static)> {
+        match *self {
+            Io(ref err) => Some(&*err),
+            Utf8Parsing(ref err) => Some(&*err),
+            _ => None,
+        }
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(err: io::Error) -> Error {
+        Error::Io(err)
+    }
+}
+
+impl From<FromUtf8Error> for Error {
+    fn from(err: FromUtf8Error) -> Error {
+        Utf8Parsing(err)
+    }
+}

src/transport/sendmail/mod.rs

@@ -0,0 +1,352 @@
+//! The sendmail transport sends the email using the local sendmail command.
+//!
+//! ## Sync example
+//!
+//! ```rust
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "sendmail-transport", feature = "builder"))]
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! # use lettre::{Message, Transport, SendmailTransport};
+//!
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let sender = SendmailTransport::new();
+//! let result = sender.send(&email);
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//!
+//! # #[cfg(not(all(feature = "sendmail-transport", feature = "builder")))]
+//! # fn main() {}
+//! ```
+//!
+//! ## Async tokio 0.2 example
+//!
+//! ```rust,no_run
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "tokio02", feature = "sendmail-transport", feature = "builder"))]
+//! # async fn run() -> Result<(), Box<dyn Error>> {
+//! use lettre::{Message, AsyncTransport, Tokio02Executor, AsyncSendmailTransport, SendmailTransport};
+//!
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let sender = AsyncSendmailTransport::<Tokio02Executor>::new();
+//! let result = sender.send(email).await;
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! ## Async tokio 1.x example
+//!
+//! ```rust,no_run
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "tokio1", feature = "sendmail-transport", feature = "builder"))]
+//! # async fn run() -> Result<(), Box<dyn Error>> {
+//! use lettre::{Message, AsyncTransport, Tokio1Executor, AsyncSendmailTransport, SendmailTransport};
+//!
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let sender = AsyncSendmailTransport::<Tokio1Executor>::new();
+//! let result = sender.send(email).await;
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! ## Async async-std 1.x example
+//!
+//!```rust,no_run
+//! # use std::error::Error;
+//!
+//! # #[cfg(all(feature = "async-std1", feature = "sendmail-transport", feature = "builder"))]
+//! # async fn run() -> Result<(), Box<dyn Error>> {
+//! use lettre::{Message, AsyncTransport, AsyncStd1Executor, AsyncSendmailTransport};
+//!
+//! let email = Message::builder()
+//!     .from("NoBody <nobody@domain.tld>".parse()?)
+//!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
+//!     .to("Hei <hei@domain.tld>".parse()?)
+//!     .subject("Happy new year")
+//!     .body(String::from("Be happy!"))?;
+//!
+//! let sender = AsyncSendmailTransport::<AsyncStd1Executor>::new();
+//! let result = sender.send(email).await;
+//! assert!(result.is_ok());
+//! # Ok(())
+//! # }
+//! ```
+
+pub use self::error::Error;
+#[cfg(feature = "async-std1")]
+use crate::AsyncStd1Executor;
+#[cfg(feature = "tokio02")]
+use crate::Tokio02Executor;
+#[cfg(feature = "tokio1")]
+use crate::Tokio1Executor;
+use crate::{address::Envelope, Transport};
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use crate::{AsyncTransport, Executor};
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use async_trait::async_trait;
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+use std::marker::PhantomData;
+use std::{
+    ffi::OsString,
+    io::prelude::*,
+    process::{Command, Stdio},
+};
+
+mod error;
+
+const DEFAUT_SENDMAIL: &str = "/usr/sbin/sendmail";
+
+/// Sends an email using the `sendmail` command
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct SendmailTransport {
+    command: OsString,
+}
+
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+pub struct AsyncSendmailTransport<E: Executor> {
+    inner: SendmailTransport,
+    marker_: PhantomData<E>,
+}
+
+impl SendmailTransport {
+    /// Creates a new transport with the default `/usr/sbin/sendmail` command
+    pub fn new() -> SendmailTransport {
+        SendmailTransport {
+            command: DEFAUT_SENDMAIL.into(),
+        }
+    }
+
+    /// Creates a new transport to the given sendmail command
+    pub fn new_with_command<S: Into<OsString>>(command: S) -> SendmailTransport {
+        SendmailTransport {
+            command: command.into(),
+        }
+    }
+
+    fn command(&self, envelope: &Envelope) -> Command {
+        let mut c = Command::new(&self.command);
+        c.arg("-i");
+        if let Some(from) = envelope.from() {
+            c.arg("-f").arg(from);
+        }
+        c.arg("--")
+            .args(envelope.to())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped());
+        c
+    }
+}
+
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+impl<E> AsyncSendmailTransport<E>
+where
+    E: Executor,
+{
+    /// Creates a new transport with the default `/usr/sbin/sendmail` command
+    pub fn new() -> Self {
+        Self {
+            inner: SendmailTransport::new(),
+            marker_: PhantomData,
+        }
+    }
+
+    /// Creates a new transport to the given sendmail command
+    pub fn new_with_command<S: Into<OsString>>(command: S) -> Self {
+        Self {
+            inner: SendmailTransport::new_with_command(command),
+            marker_: PhantomData,
+        }
+    }
+
+    #[cfg(feature = "tokio02")]
+    fn tokio02_command(&self, envelope: &Envelope) -> tokio02_crate::process::Command {
+        use tokio02_crate::process::Command;
+
+        let mut c = Command::new(&self.inner.command);
+        c.kill_on_drop(true);
+        c.arg("-i");
+        if let Some(from) = envelope.from() {
+            c.arg("-f").arg(from);
+        }
+        c.arg("--")
+            .args(envelope.to())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped());
+        c
+    }
+
+    #[cfg(feature = "tokio1")]
+    fn tokio1_command(&self, envelope: &Envelope) -> tokio1_crate::process::Command {
+        use tokio1_crate::process::Command;
+
+        let mut c = Command::new(&self.inner.command);
+        c.kill_on_drop(true);
+        c.arg("-i");
+        if let Some(from) = envelope.from() {
+            c.arg("-f").arg(from);
+        }
+        c.arg("--")
+            .args(envelope.to())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped());
+        c
+    }
+
+    #[cfg(feature = "async-std1")]
+    fn async_std_command(&self, envelope: &Envelope) -> async_std::process::Command {
+        use async_std::process::Command;
+
+        let mut c = Command::new(&self.inner.command);
+        // TODO: figure out why enabling this kills it earlier
+        // c.kill_on_drop(true);
+        c.arg("-i");
+        if let Some(from) = envelope.from() {
+            c.arg("-f").arg(from);
+        }
+        c.arg("--")
+            .args(envelope.to())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped());
+        c
+    }
+}
+
+impl Default for SendmailTransport {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
+impl<E> Default for AsyncSendmailTransport<E>
+where
+    E: Executor,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Transport for SendmailTransport {
+    type Ok = ();
+    type Error = Error;
+
+    fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        // Spawn the sendmail command
+        let mut process = self.command(envelope).spawn()?;
+
+        process.stdin.as_mut().unwrap().write_all(email)?;
+        let output = process.wait_with_output()?;
+
+        if output.status.success() {
+            Ok(())
+        } else {
+            Err(error::Error::Client(String::from_utf8(output.stderr)?))
+        }
+    }
+}
+
+#[cfg(feature = "async-std1")]
+#[async_trait]
+impl AsyncTransport for AsyncSendmailTransport<AsyncStd1Executor> {
+    type Ok = ();
+    type Error = Error;
+
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        use async_std::io::prelude::WriteExt;
+
+        let mut command = self.async_std_command(envelope);
+
+        // Spawn the sendmail command
+        let mut process = command.spawn()?;
+
+        process.stdin.as_mut().unwrap().write_all(&email).await?;
+        let output = process.output().await?;
+
+        if output.status.success() {
+            Ok(())
+        } else {
+            Err(Error::Client(String::from_utf8(output.stderr)?))
+        }
+    }
+}
+
+#[cfg(feature = "tokio02")]
+#[async_trait]
+impl AsyncTransport for AsyncSendmailTransport<Tokio02Executor> {
+    type Ok = ();
+    type Error = Error;
+
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        use tokio02_crate::io::AsyncWriteExt;
+
+        let mut command = self.tokio02_command(envelope);
+
+        // Spawn the sendmail command
+        let mut process = command.spawn()?;
+
+        process.stdin.as_mut().unwrap().write_all(&email).await?;
+        let output = process.wait_with_output().await?;
+
+        if output.status.success() {
+            Ok(())
+        } else {
+            Err(Error::Client(String::from_utf8(output.stderr)?))
+        }
+    }
+}
+
+#[cfg(feature = "tokio1")]
+#[async_trait]
+impl AsyncTransport for AsyncSendmailTransport<Tokio1Executor> {
+    type Ok = ();
+    type Error = Error;
+
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        use tokio1_crate::io::AsyncWriteExt;
+
+        let mut command = self.tokio1_command(envelope);
+
+        // Spawn the sendmail command
+        let mut process = command.spawn()?;
+
+        process.stdin.as_mut().unwrap().write_all(&email).await?;
+        let output = process.wait_with_output().await?;
+
+        if output.status.success() {
+            Ok(())
+        } else {
+            Err(Error::Client(String::from_utf8(output.stderr)?))
+        }
+    }
+}

src/transport/smtp/async_transport.rs

@@ -0,0 +1,273 @@
+use std::marker::PhantomData;
+
+use async_trait::async_trait;
+
+use super::{
+    client::AsyncSmtpConnection, ClientId, Credentials, Error, Mechanism, Response, SmtpInfo,
+};
+#[cfg(feature = "async-std1")]
+use crate::AsyncStd1Executor;
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+use crate::AsyncTransport;
+#[cfg(feature = "tokio02")]
+use crate::Tokio02Executor;
+#[cfg(feature = "tokio1")]
+use crate::Tokio1Executor;
+use crate::{Envelope, Executor};
+
+#[allow(missing_debug_implementations)]
+pub struct AsyncSmtpTransport<E> {
+    // TODO: pool
+    inner: AsyncSmtpClient<E>,
+}
+
+#[cfg(feature = "tokio02")]
+#[async_trait]
+impl AsyncTransport for AsyncSmtpTransport<Tokio02Executor> {
+    type Ok = Response;
+    type Error = Error;
+
+    /// Sends an email
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        let mut conn = self.inner.connection().await?;
+
+        let result = conn.send(envelope, email).await?;
+
+        conn.quit().await?;
+
+        Ok(result)
+    }
+}
+
+#[cfg(feature = "tokio1")]
+#[async_trait]
+impl AsyncTransport for AsyncSmtpTransport<Tokio1Executor> {
+    type Ok = Response;
+    type Error = Error;
+
+    /// Sends an email
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        let mut conn = self.inner.connection().await?;
+
+        let result = conn.send(envelope, email).await?;
+
+        conn.quit().await?;
+
+        Ok(result)
+    }
+}
+
+#[cfg(feature = "async-std1")]
+#[async_trait]
+impl AsyncTransport for AsyncSmtpTransport<AsyncStd1Executor> {
+    type Ok = Response;
+    type Error = Error;
+
+    /// Sends an email
+    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        let mut conn = self.inner.connection().await?;
+
+        let result = conn.send(envelope, email).await?;
+
+        conn.quit().await?;
+
+        Ok(result)
+    }
+}
+
+impl<E> AsyncSmtpTransport<E>
+where
+    E: Executor,
+{
+    /// Simple and secure transport, using TLS connections to communicate with the SMTP server
+    ///
+    /// The right option for most SMTP servers.
+    ///
+    /// Creates an encrypted transport over submissions port, using the provided domain
+    /// to validate TLS certificates.
+    #[cfg(any(
+        feature = "tokio02-native-tls",
+        feature = "tokio02-rustls-tls",
+        feature = "tokio1-native-tls",
+        feature = "tokio1-rustls-tls",
+        feature = "async-std1-native-tls",
+        feature = "async-std1-rustls-tls"
+    ))]
+    pub fn relay(relay: &str) -> Result<AsyncSmtpTransportBuilder, Error> {
+        use super::{Tls, TlsParameters, SUBMISSIONS_PORT};
+
+        let tls_parameters = TlsParameters::new(relay.into())?;
+
+        Ok(Self::builder_dangerous(relay)
+            .port(SUBMISSIONS_PORT)
+            .tls(Tls::Wrapper(tls_parameters)))
+    }
+
+    /// Simple an secure transport, using STARTTLS to obtain encrypted connections
+    ///
+    /// Alternative to [`AsyncSmtpTransport::relay`](#method.relay), for SMTP servers
+    /// that don't take SMTPS connections.
+    ///
+    /// Creates an encrypted transport over submissions port, by first connecting using
+    /// an unencrypted connection and then upgrading it with STARTTLS. The provided
+    /// domain is used to validate TLS certificates.
+    ///
+    /// An error is returned if the connection can't be upgraded. No credentials
+    /// or emails will be sent to the server, protecting from downgrade attacks.
+    #[cfg(any(
+        feature = "tokio02-native-tls",
+        feature = "tokio02-rustls-tls",
+        feature = "tokio1-native-tls",
+        feature = "tokio1-rustls-tls",
+        feature = "async-std1-native-tls",
+        feature = "async-std1-rustls-tls"
+    ))]
+    pub fn starttls_relay(relay: &str) -> Result<AsyncSmtpTransportBuilder, Error> {
+        use super::{Tls, TlsParameters, SUBMISSION_PORT};
+
+        let tls_parameters = TlsParameters::new(relay.into())?;
+
+        Ok(Self::builder_dangerous(relay)
+            .port(SUBMISSION_PORT)
+            .tls(Tls::Required(tls_parameters)))
+    }
+
+    /// Creates a new local SMTP client to port 25
+    ///
+    /// Shortcut for local unencrypted relay (typical local email daemon that will handle relaying)
+    pub fn unencrypted_localhost() -> AsyncSmtpTransport<E> {
+        Self::builder_dangerous("localhost").build()
+    }
+
+    /// Creates a new SMTP client
+    ///
+    /// Defaults are:
+    ///
+    /// * No authentication
+    /// * No TLS
+    /// * Port 25
+    ///
+    /// Consider using [`AsyncSmtpTransport::relay`](#method.relay) or
+    /// [`AsyncSmtpTransport::starttls_relay`](#method.starttls_relay) instead,
+    /// if possible.
+    pub fn builder_dangerous<T: Into<String>>(server: T) -> AsyncSmtpTransportBuilder {
+        let new = SmtpInfo {
+            server: server.into(),
+            ..Default::default()
+        };
+        AsyncSmtpTransportBuilder { info: new }
+    }
+}
+
+impl<E> Clone for AsyncSmtpTransport<E>
+where
+    E: Executor,
+{
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+        }
+    }
+}
+
+/// Contains client configuration.
+/// Instances of this struct can be created using functions of [`AsyncSmtpTransport`].
+#[allow(missing_debug_implementations)]
+#[derive(Clone)]
+pub struct AsyncSmtpTransportBuilder {
+    info: SmtpInfo,
+}
+
+/// Builder for the SMTP `AsyncSmtpTransport`
+impl AsyncSmtpTransportBuilder {
+    /// Set the name used during EHLO
+    pub fn hello_name(mut self, name: ClientId) -> Self {
+        self.info.hello_name = name;
+        self
+    }
+
+    /// Set the authentication mechanism to use
+    pub fn credentials(mut self, credentials: Credentials) -> Self {
+        self.info.credentials = Some(credentials);
+        self
+    }
+
+    /// Set the authentication mechanism to use
+    pub fn authentication(mut self, mechanisms: Vec<Mechanism>) -> Self {
+        self.info.authentication = mechanisms;
+        self
+    }
+
+    /// Set the port to use
+    pub fn port(mut self, port: u16) -> Self {
+        self.info.port = port;
+        self
+    }
+
+    /// Set the TLS settings to use
+    #[cfg(any(
+        feature = "tokio02-native-tls",
+        feature = "tokio02-rustls-tls",
+        feature = "tokio1-native-tls",
+        feature = "tokio1-rustls-tls",
+        feature = "async-std1-native-tls",
+        feature = "async-std1-rustls-tls"
+    ))]
+    pub fn tls(mut self, tls: super::Tls) -> Self {
+        self.info.tls = tls;
+        self
+    }
+
+    /// Build the transport (with default pool if enabled)
+    pub fn build<E>(self) -> AsyncSmtpTransport<E>
+    where
+        E: Executor,
+    {
+        let client = AsyncSmtpClient {
+            info: self.info,
+            marker_: PhantomData,
+        };
+        AsyncSmtpTransport { inner: client }
+    }
+}
+
+/// Build client
+pub struct AsyncSmtpClient<C> {
+    info: SmtpInfo,
+    marker_: PhantomData<C>,
+}
+
+impl<E> AsyncSmtpClient<E>
+where
+    E: Executor,
+{
+    /// Creates a new connection directly usable to send emails
+    ///
+    /// Handles encryption and authentication
+    pub async fn connection(&self) -> Result<AsyncSmtpConnection, Error> {
+        let mut conn = E::connect(
+            &self.info.server,
+            self.info.port,
+            &self.info.hello_name,
+            &self.info.tls,
+        )
+        .await?;
+
+        if let Some(credentials) = &self.info.credentials {
+            conn.auth(&self.info.authentication, &credentials).await?;
+        }
+        Ok(conn)
+    }
+}
+
+impl<E> AsyncSmtpClient<E>
+where
+    E: Executor,
+{
+    fn clone(&self) -> Self {
+        Self {
+            info: self.info.clone(),
+            marker_: PhantomData,
+        }
+    }
+}

src/transport/smtp/authentication.rs

@@ -1,37 +1,15 @@
 //! Provides limited SASL authentication mechanisms
 
-use smtp::error::Error;
+use crate::transport::smtp::error::Error;
 use std::fmt::{self, Display, Formatter};
 
-/// Accepted authentication mechanisms on an encrypted connection
+/// Accepted authentication mechanisms
 /// Trying LOGIN last as it is deprecated.
-pub const DEFAULT_ENCRYPTED_MECHANISMS: &[Mechanism] = &[Mechanism::Plain, Mechanism::Login];
-
-/// Accepted authentication mechanisms on an unencrypted connection
-pub const DEFAULT_UNENCRYPTED_MECHANISMS: &[Mechanism] = &[];
-
-/// Convertable to user credentials
-pub trait IntoCredentials {
-    /// Converts to a `Credentials` struct
-    fn into_credentials(self) -> Credentials;
-}
-
-impl IntoCredentials for Credentials {
-    fn into_credentials(self) -> Credentials {
-        self
-    }
-}
-
-impl<S: Into<String>, T: Into<String>> IntoCredentials for (S, T) {
-    fn into_credentials(self) -> Credentials {
-        let (username, password) = self;
-        Credentials::new(username.into(), password.into())
-    }
-}
+pub const DEFAULT_MECHANISMS: &[Mechanism] = &[Mechanism::Plain, Mechanism::Login];
 
 /// Contains user credentials
 #[derive(PartialEq, Eq, Clone, Hash, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Credentials {
     authentication_identity: String,
     secret: String,
@@ -47,33 +25,40 @@ impl Credentials {
     }
 }
 
+impl<S, T> From<(S, T)> for Credentials
+where
+    S: Into<String>,
+    T: Into<String>,
+{
+    fn from((username, password): (S, T)) -> Self {
+        Credentials::new(username.into(), password.into())
+    }
+}
+
 /// Represents authentication mechanisms
 #[derive(PartialEq, Eq, Copy, Clone, Hash, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum Mechanism {
-    /// PLAIN authentication mechanism
-    /// RFC 4616: https://tools.ietf.org/html/rfc4616
+    /// PLAIN authentication mechanism, defined in
+    /// [RFC 4616](https://tools.ietf.org/html/rfc4616)
     Plain,
     /// LOGIN authentication mechanism
     /// Obsolete but needed for some providers (like office365)
-    /// https://www.ietf.org/archive/id/draft-murchison-sasl-login-00.txt
+    ///
+    /// Defined in [draft-murchison-sasl-login-00](https://www.ietf.org/archive/id/draft-murchison-sasl-login-00.txt).
     Login,
-    /// Non-standard XOAUTH2 mechanism
-    /// https://developers.google.com/gmail/imap/xoauth2-protocol
+    /// Non-standard XOAUTH2 mechanism, defined in
+    /// [xoauth2-protocol](https://developers.google.com/gmail/imap/xoauth2-protocol)
     Xoauth2,
 }
 
 impl Display for Mechanism {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(
-            f,
-            "{}",
-            match *self {
-                Mechanism::Plain => "PLAIN",
-                Mechanism::Login => "LOGIN",
-                Mechanism::Xoauth2 => "XOAUTH2",
-            }
-        )
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.write_str(match *self {
+            Mechanism::Plain => "PLAIN",
+            Mechanism::Login => "LOGIN",
+            Mechanism::Xoauth2 => "XOAUTH2",
+        })
     }
 }
 
@@ -175,4 +160,12 @@ mod test {
         );
         assert!(mechanism.response(&credentials, Some("test")).is_err());
     }
+
+    #[test]
+    fn test_from_user_pass_for_credentials() {
+        assert_eq!(
+            Credentials::new("alice".to_string(), "wonderland".to_string()),
+            Credentials::from(("alice", "wonderland"))
+        );
+    }
 }

src/transport/smtp/client/async_connection.rs

@@ -0,0 +1,319 @@
+use std::{fmt::Display, io};
+
+use futures_util::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
+
+use super::{AsyncNetworkStream, ClientCodec, TlsParameters};
+use crate::{
+    transport::smtp::{
+        authentication::{Credentials, Mechanism},
+        commands::*,
+        error::Error,
+        extension::{ClientId, Extension, MailBodyParameter, MailParameter, ServerInfo},
+        response::{parse_response, Response},
+    },
+    Envelope,
+};
+
+#[cfg(feature = "tracing")]
+use super::escape_crlf;
+
+macro_rules! try_smtp (
+    ($err: expr, $client: ident) => ({
+        match $err {
+            Ok(val) => val,
+            Err(err) => {
+                $client.abort().await;
+                return Err(From::from(err))
+            },
+        }
+    })
+);
+
+/// Structure that implements the SMTP client
+pub struct AsyncSmtpConnection {
+    /// TCP stream between client and server
+    /// Value is None before connection
+    stream: BufReader<AsyncNetworkStream>,
+    /// Panic state
+    panic: bool,
+    /// Information about the server
+    server_info: ServerInfo,
+}
+
+impl AsyncSmtpConnection {
+    pub fn server_info(&self) -> &ServerInfo {
+        &self.server_info
+    }
+
+    /// Connects to the configured server
+    ///
+    /// Sends EHLO and parses server information
+    #[cfg(feature = "tokio02")]
+    pub async fn connect_tokio02(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls_parameters: Option<TlsParameters>,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        let stream = AsyncNetworkStream::connect_tokio02(hostname, port, tls_parameters).await?;
+        Self::connect_impl(stream, hello_name).await
+    }
+
+    /// Connects to the configured server
+    ///
+    /// Sends EHLO and parses server information
+    #[cfg(feature = "tokio1")]
+    pub async fn connect_tokio1(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls_parameters: Option<TlsParameters>,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        let stream = AsyncNetworkStream::connect_tokio1(hostname, port, tls_parameters).await?;
+        Self::connect_impl(stream, hello_name).await
+    }
+
+    /// Connects to the configured server
+    ///
+    /// Sends EHLO and parses server information
+    #[cfg(feature = "async-std1")]
+    pub async fn connect_asyncstd1(
+        hostname: &str,
+        port: u16,
+        hello_name: &ClientId,
+        tls_parameters: Option<TlsParameters>,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        let stream = AsyncNetworkStream::connect_asyncstd1(hostname, port, tls_parameters).await?;
+        Self::connect_impl(stream, hello_name).await
+    }
+
+    async fn connect_impl(
+        stream: AsyncNetworkStream,
+        hello_name: &ClientId,
+    ) -> Result<AsyncSmtpConnection, Error> {
+        let stream = BufReader::new(stream);
+        let mut conn = AsyncSmtpConnection {
+            stream,
+            panic: false,
+            server_info: ServerInfo::default(),
+        };
+        // TODO log
+        let _response = conn.read_response().await?;
+
+        conn.ehlo(hello_name).await?;
+
+        // Print server information
+        #[cfg(feature = "tracing")]
+        tracing::debug!("server {}", conn.server_info);
+        Ok(conn)
+    }
+
+    pub async fn send(&mut self, envelope: &Envelope, email: &[u8]) -> Result<Response, Error> {
+        // Mail
+        let mut mail_options = vec![];
+
+        // Internationalization handling
+        //
+        // * 8BITMIME: https://tools.ietf.org/html/rfc6152
+        // * SMTPUTF8: https://tools.ietf.org/html/rfc653
+
+        // Check for non-ascii addresses and use the SMTPUTF8 option if any.
+        if envelope.has_non_ascii_addresses() {
+            if !self.server_info().supports_feature(Extension::SmtpUtfEight) {
+                // don't try to send non-ascii addresses (per RFC)
+                return Err(Error::Client(
+                    "Envelope contains non-ascii chars but server does not support SMTPUTF8",
+                ));
+            }
+            mail_options.push(MailParameter::SmtpUtfEight);
+        }
+
+        // Check for non-ascii content in message
+        if !email.is_ascii() {
+            if !self.server_info().supports_feature(Extension::EightBitMime) {
+                return Err(Error::Client(
+                    "Message contains non-ascii chars but server does not support 8BITMIME",
+                ));
+            }
+            mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
+        }
+
+        try_smtp!(
+            self.command(Mail::new(envelope.from().cloned(), mail_options))
+                .await,
+            self
+        );
+
+        // Recipient
+        for to_address in envelope.to() {
+            try_smtp!(
+                self.command(Rcpt::new(to_address.clone(), vec![])).await,
+                self
+            );
+        }
+
+        // Data
+        try_smtp!(self.command(Data).await, self);
+
+        // Message content
+        let result = try_smtp!(self.message(email).await, self);
+        Ok(result)
+    }
+
+    pub fn has_broken(&self) -> bool {
+        self.panic
+    }
+
+    pub fn can_starttls(&self) -> bool {
+        !self.is_encrypted() && self.server_info.supports_feature(Extension::StartTls)
+    }
+
+    #[allow(unused_variables)]
+    pub async fn starttls(
+        &mut self,
+        tls_parameters: TlsParameters,
+        hello_name: &ClientId,
+    ) -> Result<(), Error> {
+        if self.server_info.supports_feature(Extension::StartTls) {
+            try_smtp!(self.command(Starttls).await, self);
+            try_smtp!(
+                self.stream.get_mut().upgrade_tls(tls_parameters).await,
+                self
+            );
+            #[cfg(feature = "tracing")]
+            tracing::debug!("connection encrypted");
+            // Send EHLO again
+            try_smtp!(self.ehlo(hello_name).await, self);
+            Ok(())
+        } else {
+            Err(Error::Client("STARTTLS is not supported on this server"))
+        }
+    }
+
+    /// Send EHLO and update server info
+    async fn ehlo(&mut self, hello_name: &ClientId) -> Result<(), Error> {
+        let ehlo_response = try_smtp!(self.command(Ehlo::new(hello_name.clone())).await, self);
+        self.server_info = try_smtp!(ServerInfo::from_response(&ehlo_response), self);
+        Ok(())
+    }
+
+    pub async fn quit(&mut self) -> Result<Response, Error> {
+        Ok(try_smtp!(self.command(Quit).await, self))
+    }
+
+    pub async fn abort(&mut self) {
+        // Only try to quit if we are not already broken
+        if !self.panic {
+            self.panic = true;
+            let _ = self.command(Quit).await;
+        }
+    }
+
+    /// Sets the underlying stream
+    pub fn set_stream(&mut self, stream: AsyncNetworkStream) {
+        self.stream = BufReader::new(stream);
+    }
+
+    /// Tells if the underlying stream is currently encrypted
+    pub fn is_encrypted(&self) -> bool {
+        self.stream.get_ref().is_encrypted()
+    }
+
+    /// Checks if the server is connected using the NOOP SMTP command
+    pub async fn test_connected(&mut self) -> bool {
+        self.command(Noop).await.is_ok()
+    }
+
+    /// Sends an AUTH command with the given mechanism, and handles challenge if needed
+    pub async fn auth(
+        &mut self,
+        mechanisms: &[Mechanism],
+        credentials: &Credentials,
+    ) -> Result<Response, Error> {
+        let mechanism = self
+            .server_info
+            .get_auth_mechanism(mechanisms)
+            .ok_or(Error::Client(
+                "No compatible authentication mechanism was found",
+            ))?;
+
+        // Limit challenges to avoid blocking
+        let mut challenges = 10;
+        let mut response = self
+            .command(Auth::new(mechanism, credentials.clone(), None)?)
+            .await?;
+
+        while challenges > 0 && response.has_code(334) {
+            challenges -= 1;
+            response = try_smtp!(
+                self.command(Auth::new_from_response(
+                    mechanism,
+                    credentials.clone(),
+                    &response,
+                )?)
+                .await,
+                self
+            );
+        }
+
+        if challenges == 0 {
+            Err(Error::ResponseParsing("Unexpected number of challenges"))
+        } else {
+            Ok(response)
+        }
+    }
+
+    /// Sends the message content
+    pub async fn message(&mut self, message: &[u8]) -> Result<Response, Error> {
+        let mut out_buf: Vec<u8> = vec![];
+        let mut codec = ClientCodec::new();
+        codec.encode(message, &mut out_buf);
+        self.write(out_buf.as_slice()).await?;
+        self.write(b"\r\n.\r\n").await?;
+        self.read_response().await
+    }
+
+    /// Sends an SMTP command
+    pub async fn command<C: Display>(&mut self, command: C) -> Result<Response, Error> {
+        self.write(command.to_string().as_bytes()).await?;
+        self.read_response().await
+    }
+
+    /// Writes a string to the server
+    async fn write(&mut self, string: &[u8]) -> Result<(), Error> {
+        self.stream.get_mut().write_all(string).await?;
+        self.stream.get_mut().flush().await?;
+
+        #[cfg(feature = "tracing")]
+        tracing::debug!("Wrote: {}", escape_crlf(&String::from_utf8_lossy(string)));
+        Ok(())
+    }
+
+    /// Gets the SMTP response
+    pub async fn read_response(&mut self) -> Result<Response, Error> {
+        let mut buffer = String::with_capacity(100);
+
+        while self.stream.read_line(&mut buffer).await? > 0 {
+            #[cfg(feature = "tracing")]
+            tracing::debug!("<< {}", escape_crlf(&buffer));
+            match parse_response(&buffer) {
+                Ok((_remaining, response)) => {
+                    if response.is_positive() {
+                        return Ok(response);
+                    }
+
+                    return Err(response.into());
+                }
+                Err(nom::Err::Failure(e)) => {
+                    return Err(Error::Parsing(e.code));
+                }
+                Err(nom::Err::Incomplete(_)) => { /* read more */ }
+                Err(nom::Err::Error(e)) => {
+                    return Err(Error::Parsing(e.code));
+                }
+            }
+        }
+
+        Err(io::Error::new(io::ErrorKind::Other, "incomplete").into())
+    }
+}

src/transport/smtp/client/async_net.rs

@@ -0,0 +1,559 @@
+#[cfg(any(
+    feature = "tokio02-rustls-tls",
+    feature = "tokio1-rustls-tls",
+    feature = "async-std1-rustls-tls"
+))]
+use std::sync::Arc;
+use std::{
+    net::SocketAddr,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+use futures_io::{
+    AsyncRead as FuturesAsyncRead, AsyncWrite as FuturesAsyncWrite, Error as IoError, ErrorKind,
+    Result as IoResult,
+};
+#[cfg(feature = "tokio02")]
+use tokio02_crate::io::{AsyncRead as _, AsyncWrite as _};
+#[cfg(feature = "tokio1")]
+use tokio1_crate::io::{AsyncRead as _, AsyncWrite as _, ReadBuf as Tokio1ReadBuf};
+
+#[cfg(feature = "async-std1")]
+use async_std::net::TcpStream as AsyncStd1TcpStream;
+#[cfg(feature = "tokio02")]
+use tokio02_crate::net::TcpStream as Tokio02TcpStream;
+#[cfg(feature = "tokio1")]
+use tokio1_crate::net::TcpStream as Tokio1TcpStream;
+
+#[cfg(feature = "async-std1-native-tls")]
+use async_native_tls::TlsStream as AsyncStd1TlsStream;
+#[cfg(feature = "tokio02-native-tls")]
+use tokio02_native_tls_crate::TlsStream as Tokio02TlsStream;
+#[cfg(feature = "tokio1-native-tls")]
+use tokio1_native_tls_crate::TlsStream as Tokio1TlsStream;
+
+#[cfg(feature = "async-std1-rustls-tls")]
+use async_rustls::client::TlsStream as AsyncStd1RustlsTlsStream;
+#[cfg(feature = "tokio02-rustls-tls")]
+use tokio02_rustls::client::TlsStream as Tokio02RustlsTlsStream;
+#[cfg(feature = "tokio1-rustls-tls")]
+use tokio1_rustls::client::TlsStream as Tokio1RustlsTlsStream;
+
+#[cfg(any(
+    feature = "tokio02-native-tls",
+    feature = "tokio02-rustls-tls",
+    feature = "tokio1-native-tls",
+    feature = "tokio1-rustls-tls",
+    feature = "async-std1-native-tls",
+    feature = "async-std1-rustls-tls"
+))]
+use super::InnerTlsParameters;
+use super::TlsParameters;
+use crate::transport::smtp::Error;
+
+/// A network stream
+pub struct AsyncNetworkStream {
+    inner: InnerAsyncNetworkStream,
+}
+
+/// Represents the different types of underlying network streams
+// usually only one TLS backend at a time is going to be enabled,
+// so clippy::large_enum_variant doesn't make sense here
+#[allow(clippy::large_enum_variant)]
+#[allow(dead_code)]
+enum InnerAsyncNetworkStream {
+    /// Plain Tokio 0.2 TCP stream
+    #[cfg(feature = "tokio02")]
+    Tokio02Tcp(Tokio02TcpStream),
+    /// Encrypted Tokio 0.2 TCP stream
+    #[cfg(feature = "tokio02-native-tls")]
+    Tokio02NativeTls(Tokio02TlsStream<Tokio02TcpStream>),
+    /// Encrypted Tokio 0.2 TCP stream
+    #[cfg(feature = "tokio02-rustls-tls")]
+    Tokio02RustlsTls(Tokio02RustlsTlsStream<Tokio02TcpStream>),
+    /// Plain Tokio 1.x TCP stream
+    #[cfg(feature = "tokio1")]
+    Tokio1Tcp(Tokio1TcpStream),
+    /// Encrypted Tokio 1.x TCP stream
+    #[cfg(feature = "tokio1-native-tls")]
+    Tokio1NativeTls(Tokio1TlsStream<Tokio1TcpStream>),
+    /// Encrypted Tokio 1.x TCP stream
+    #[cfg(feature = "tokio1-rustls-tls")]
+    Tokio1RustlsTls(Tokio1RustlsTlsStream<Tokio1TcpStream>),
+    /// Plain Tokio 1.x TCP stream
+    #[cfg(feature = "async-std1")]
+    AsyncStd1Tcp(AsyncStd1TcpStream),
+    /// Encrypted Tokio 1.x TCP stream
+    #[cfg(feature = "async-std1-native-tls")]
+    AsyncStd1NativeTls(AsyncStd1TlsStream<AsyncStd1TcpStream>),
+    /// Encrypted Tokio 1.x TCP stream
+    #[cfg(feature = "async-std1-rustls-tls")]
+    AsyncStd1RustlsTls(AsyncStd1RustlsTlsStream<AsyncStd1TcpStream>),
+    /// Can't be built
+    None,
+}
+
+impl AsyncNetworkStream {
+    fn new(inner: InnerAsyncNetworkStream) -> Self {
+        if let InnerAsyncNetworkStream::None = inner {
+            debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+        }
+
+        AsyncNetworkStream { inner }
+    }
+
+    /// Returns peer's address
+    pub fn peer_addr(&self) -> IoResult<SocketAddr> {
+        match self.inner {
+            #[cfg(feature = "tokio02")]
+            InnerAsyncNetworkStream::Tokio02Tcp(ref s) => s.peer_addr(),
+            #[cfg(feature = "tokio02-native-tls")]
+            InnerAsyncNetworkStream::Tokio02NativeTls(ref s) => {
+                s.get_ref().get_ref().get_ref().peer_addr()
+            }
+            #[cfg(feature = "tokio02-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio02RustlsTls(ref s) => s.get_ref().0.peer_addr(),
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(ref s) => s.peer_addr(),
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(ref s) => {
+                s.get_ref().get_ref().get_ref().peer_addr()
+            }
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(ref s) => s.get_ref().0.peer_addr(),
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(ref s) => s.peer_addr(),
+            #[cfg(feature = "async-std1-native-tls")]
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref s) => s.get_ref().peer_addr(),
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref s) => s.get_ref().0.peer_addr(),
+            InnerAsyncNetworkStream::None => {
+                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+                Err(IoError::new(
+                    ErrorKind::Other,
+                    "InnerAsyncNetworkStream::None must never be built",
+                ))
+            }
+        }
+    }
+
+    #[cfg(feature = "tokio02")]
+    pub async fn connect_tokio02(
+        hostname: &str,
+        port: u16,
+        tls_parameters: Option<TlsParameters>,
+    ) -> Result<AsyncNetworkStream, Error> {
+        let tcp_stream = Tokio02TcpStream::connect((hostname, port)).await?;
+
+        let mut stream = AsyncNetworkStream::new(InnerAsyncNetworkStream::Tokio02Tcp(tcp_stream));
+        if let Some(tls_parameters) = tls_parameters {
+            stream.upgrade_tls(tls_parameters).await?;
+        }
+        Ok(stream)
+    }
+
+    #[cfg(feature = "tokio1")]
+    pub async fn connect_tokio1(
+        hostname: &str,
+        port: u16,
+        tls_parameters: Option<TlsParameters>,
+    ) -> Result<AsyncNetworkStream, Error> {
+        let tcp_stream = Tokio1TcpStream::connect((hostname, port)).await?;
+
+        let mut stream = AsyncNetworkStream::new(InnerAsyncNetworkStream::Tokio1Tcp(tcp_stream));
+        if let Some(tls_parameters) = tls_parameters {
+            stream.upgrade_tls(tls_parameters).await?;
+        }
+        Ok(stream)
+    }
+
+    #[cfg(feature = "async-std1")]
+    pub async fn connect_asyncstd1(
+        hostname: &str,
+        port: u16,
+        tls_parameters: Option<TlsParameters>,
+    ) -> Result<AsyncNetworkStream, Error> {
+        let tcp_stream = AsyncStd1TcpStream::connect((hostname, port)).await?;
+
+        let mut stream = AsyncNetworkStream::new(InnerAsyncNetworkStream::AsyncStd1Tcp(tcp_stream));
+        if let Some(tls_parameters) = tls_parameters {
+            stream.upgrade_tls(tls_parameters).await?;
+        }
+        Ok(stream)
+    }
+
+    pub async fn upgrade_tls(&mut self, tls_parameters: TlsParameters) -> Result<(), Error> {
+        match &self.inner {
+            #[cfg(all(
+                feature = "tokio02",
+                not(any(feature = "tokio02-native-tls", feature = "tokio02-rustls-tls"))
+            ))]
+            InnerAsyncNetworkStream::Tokio02Tcp(_) => {
+                let _ = tls_parameters;
+                panic!("Trying to upgrade an AsyncNetworkStream without having enabled either the tokio02-native-tls or the tokio02-rustls-tls feature");
+            }
+
+            #[cfg(any(feature = "tokio02-native-tls", feature = "tokio02-rustls-tls"))]
+            InnerAsyncNetworkStream::Tokio02Tcp(_) => {
+                // get owned TcpStream
+                let tcp_stream = std::mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);
+                let tcp_stream = match tcp_stream {
+                    InnerAsyncNetworkStream::Tokio02Tcp(tcp_stream) => tcp_stream,
+                    _ => unreachable!(),
+                };
+
+                self.inner = Self::upgrade_tokio02_tls(tcp_stream, tls_parameters).await?;
+                Ok(())
+            }
+            #[cfg(all(
+                feature = "tokio1",
+                not(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))
+            ))]
+            InnerAsyncNetworkStream::Tokio1Tcp(_) => {
+                let _ = tls_parameters;
+                panic!("Trying to upgrade an AsyncNetworkStream without having enabled either the tokio1-native-tls or the tokio1-rustls-tls feature");
+            }
+
+            #[cfg(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))]
+            InnerAsyncNetworkStream::Tokio1Tcp(_) => {
+                // get owned TcpStream
+                let tcp_stream = std::mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);
+                let tcp_stream = match tcp_stream {
+                    InnerAsyncNetworkStream::Tokio1Tcp(tcp_stream) => tcp_stream,
+                    _ => unreachable!(),
+                };
+
+                self.inner = Self::upgrade_tokio1_tls(tcp_stream, tls_parameters).await?;
+                Ok(())
+            }
+            #[cfg(all(
+                feature = "async-std1",
+                not(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))
+            ))]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
+                let _ = tls_parameters;
+                panic!("Trying to upgrade an AsyncNetworkStream without having enabled either the async-std1-native-tls or the async-std1-rustls-tls feature");
+            }
+
+            #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
+                // get owned TcpStream
+                let tcp_stream = std::mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);
+                let tcp_stream = match tcp_stream {
+                    InnerAsyncNetworkStream::AsyncStd1Tcp(tcp_stream) => tcp_stream,
+                    _ => unreachable!(),
+                };
+
+                self.inner = Self::upgrade_asyncstd1_tls(tcp_stream, tls_parameters).await?;
+                Ok(())
+            }
+            _ => Ok(()),
+        }
+    }
+
+    #[allow(unused_variables)]
+    #[cfg(any(feature = "tokio02-native-tls", feature = "tokio02-rustls-tls"))]
+    async fn upgrade_tokio02_tls(
+        tcp_stream: Tokio02TcpStream,
+        mut tls_parameters: TlsParameters,
+    ) -> Result<InnerAsyncNetworkStream, Error> {
+        let domain = std::mem::take(&mut tls_parameters.domain);
+
+        match tls_parameters.connector {
+            #[cfg(feature = "native-tls")]
+            InnerTlsParameters::NativeTls(connector) => {
+                #[cfg(not(feature = "tokio02-native-tls"))]
+                panic!("built without the tokio02-native-tls feature");
+
+                #[cfg(feature = "tokio02-native-tls")]
+                return {
+                    use tokio02_native_tls_crate::TlsConnector;
+
+                    let connector = TlsConnector::from(connector);
+                    let stream = connector.connect(&domain, tcp_stream).await?;
+                    Ok(InnerAsyncNetworkStream::Tokio02NativeTls(stream))
+                };
+            }
+            #[cfg(feature = "rustls-tls")]
+            InnerTlsParameters::RustlsTls(config) => {
+                #[cfg(not(feature = "tokio02-rustls-tls"))]
+                panic!("built without the tokio02-rustls-tls feature");
+
+                #[cfg(feature = "tokio02-rustls-tls")]
+                return {
+                    use tokio02_rustls::{webpki::DNSNameRef, TlsConnector};
+
+                    let domain = DNSNameRef::try_from_ascii_str(&domain)?;
+
+                    let connector = TlsConnector::from(Arc::new(config));
+                    let stream = connector.connect(domain, tcp_stream).await?;
+                    Ok(InnerAsyncNetworkStream::Tokio02RustlsTls(stream))
+                };
+            }
+        }
+    }
+
+    #[allow(unused_variables)]
+    #[cfg(any(feature = "tokio1-native-tls", feature = "tokio1-rustls-tls"))]
+    async fn upgrade_tokio1_tls(
+        tcp_stream: Tokio1TcpStream,
+        mut tls_parameters: TlsParameters,
+    ) -> Result<InnerAsyncNetworkStream, Error> {
+        let domain = std::mem::take(&mut tls_parameters.domain);
+
+        match tls_parameters.connector {
+            #[cfg(feature = "native-tls")]
+            InnerTlsParameters::NativeTls(connector) => {
+                #[cfg(not(feature = "tokio1-native-tls"))]
+                panic!("built without the tokio1-native-tls feature");
+
+                #[cfg(feature = "tokio1-native-tls")]
+                return {
+                    use tokio1_native_tls_crate::TlsConnector;
+
+                    let connector = TlsConnector::from(connector);
+                    let stream = connector.connect(&domain, tcp_stream).await?;
+                    Ok(InnerAsyncNetworkStream::Tokio1NativeTls(stream))
+                };
+            }
+            #[cfg(feature = "rustls-tls")]
+            InnerTlsParameters::RustlsTls(config) => {
+                #[cfg(not(feature = "tokio1-rustls-tls"))]
+                panic!("built without the tokio1-rustls-tls feature");
+
+                #[cfg(feature = "tokio1-rustls-tls")]
+                return {
+                    use tokio1_rustls::{webpki::DNSNameRef, TlsConnector};
+
+                    let domain = DNSNameRef::try_from_ascii_str(&domain)?;
+
+                    let connector = TlsConnector::from(Arc::new(config));
+                    let stream = connector.connect(domain, tcp_stream).await?;
+                    Ok(InnerAsyncNetworkStream::Tokio1RustlsTls(stream))
+                };
+            }
+        }
+    }
+
+    #[allow(unused_variables)]
+    #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+    async fn upgrade_asyncstd1_tls(
+        tcp_stream: AsyncStd1TcpStream,
+        mut tls_parameters: TlsParameters,
+    ) -> Result<InnerAsyncNetworkStream, Error> {
+        let domain = std::mem::take(&mut tls_parameters.domain);
+
+        match tls_parameters.connector {
+            #[cfg(feature = "native-tls")]
+            InnerTlsParameters::NativeTls(connector) => {
+                panic!("native-tls isn't supported with async-std yet. See https://github.com/lettre/lettre/pull/531#issuecomment-757893531");
+
+                /*
+                #[cfg(not(feature = "async-std1-native-tls"))]
+                panic!("built without the async-std1-native-tls feature");
+
+                #[cfg(feature = "async-std1-native-tls")]
+                return {
+                    use async_native_tls::TlsConnector;
+
+                    // TODO: fix
+                    let connector: TlsConnector = todo!();
+                    // let connector = TlsConnector::from(connector);
+                    let stream = connector.connect(&domain, tcp_stream).await?;
+                    Ok(InnerAsyncNetworkStream::AsyncStd1NativeTls(stream))
+                };
+                */
+            }
+            #[cfg(feature = "rustls-tls")]
+            InnerTlsParameters::RustlsTls(config) => {
+                #[cfg(not(feature = "async-std1-rustls-tls"))]
+                panic!("built without the async-std1-rustls-tls feature");
+
+                #[cfg(feature = "async-std1-rustls-tls")]
+                return {
+                    use async_rustls::{webpki::DNSNameRef, TlsConnector};
+
+                    let domain = DNSNameRef::try_from_ascii_str(&domain)?;
+
+                    let connector = TlsConnector::from(Arc::new(config));
+                    let stream = connector.connect(domain, tcp_stream).await?;
+                    Ok(InnerAsyncNetworkStream::AsyncStd1RustlsTls(stream))
+                };
+            }
+        }
+    }
+
+    pub fn is_encrypted(&self) -> bool {
+        match self.inner {
+            #[cfg(feature = "tokio02")]
+            InnerAsyncNetworkStream::Tokio02Tcp(_) => false,
+            #[cfg(feature = "tokio02-native-tls")]
+            InnerAsyncNetworkStream::Tokio02NativeTls(_) => true,
+            #[cfg(feature = "tokio02-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio02RustlsTls(_) => true,
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(_) => false,
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(_) => true,
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(_) => true,
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(_) => false,
+            #[cfg(feature = "async-std1-native-tls")]
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(_) => true,
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(_) => true,
+            InnerAsyncNetworkStream::None => false,
+        }
+    }
+}
+
+impl FuturesAsyncRead for AsyncNetworkStream {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut [u8],
+    ) -> Poll<IoResult<usize>> {
+        match self.inner {
+            #[cfg(feature = "tokio02")]
+            InnerAsyncNetworkStream::Tokio02Tcp(ref mut s) => Pin::new(s).poll_read(cx, buf),
+            #[cfg(feature = "tokio02-native-tls")]
+            InnerAsyncNetworkStream::Tokio02NativeTls(ref mut s) => Pin::new(s).poll_read(cx, buf),
+            #[cfg(feature = "tokio02-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio02RustlsTls(ref mut s) => Pin::new(s).poll_read(cx, buf),
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => {
+                let mut b = Tokio1ReadBuf::new(buf);
+                match Pin::new(s).poll_read(cx, &mut b) {
+                    Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
+                    Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
+                    Poll::Pending => Poll::Pending,
+                }
+            }
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => {
+                let mut b = Tokio1ReadBuf::new(buf);
+                match Pin::new(s).poll_read(cx, &mut b) {
+                    Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
+                    Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
+                    Poll::Pending => Poll::Pending,
+                }
+            }
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => {
+                let mut b = Tokio1ReadBuf::new(buf);
+                match Pin::new(s).poll_read(cx, &mut b) {
+                    Poll::Ready(Ok(())) => Poll::Ready(Ok(b.filled().len())),
+                    Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
+                    Poll::Pending => Poll::Pending,
+                }
+            }
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_read(cx, buf),
+            #[cfg(feature = "async-std1-native-tls")]
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => {
+                Pin::new(s).poll_read(cx, buf)
+            }
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => {
+                Pin::new(s).poll_read(cx, buf)
+            }
+            InnerAsyncNetworkStream::None => {
+                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+                Poll::Ready(Ok(0))
+            }
+        }
+    }
+}
+
+impl FuturesAsyncWrite for AsyncNetworkStream {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<IoResult<usize>> {
+        match self.inner {
+            #[cfg(feature = "tokio02")]
+            InnerAsyncNetworkStream::Tokio02Tcp(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "tokio02-native-tls")]
+            InnerAsyncNetworkStream::Tokio02NativeTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "tokio02-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio02RustlsTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_write(cx, buf),
+            #[cfg(feature = "async-std1-native-tls")]
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => {
+                Pin::new(s).poll_write(cx, buf)
+            }
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => {
+                Pin::new(s).poll_write(cx, buf)
+            }
+            InnerAsyncNetworkStream::None => {
+                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+                Poll::Ready(Ok(0))
+            }
+        }
+    }
+
+    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<IoResult<()>> {
+        match self.inner {
+            #[cfg(feature = "tokio02")]
+            InnerAsyncNetworkStream::Tokio02Tcp(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "tokio02-native-tls")]
+            InnerAsyncNetworkStream::Tokio02NativeTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "tokio02-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio02RustlsTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "async-std1-native-tls")]
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::None => {
+                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+                Poll::Ready(Ok(()))
+            }
+        }
+    }
+
+    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<IoResult<()>> {
+        match self.inner {
+            #[cfg(feature = "tokio02")]
+            InnerAsyncNetworkStream::Tokio02Tcp(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            #[cfg(feature = "tokio02-native-tls")]
+            InnerAsyncNetworkStream::Tokio02NativeTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            #[cfg(feature = "tokio02-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio02RustlsTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(ref mut s) => Pin::new(s).poll_shutdown(cx),
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(ref mut s) => Pin::new(s).poll_close(cx),
+            #[cfg(feature = "async-std1-native-tls")]
+            InnerAsyncNetworkStream::AsyncStd1NativeTls(ref mut s) => Pin::new(s).poll_close(cx),
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(ref mut s) => Pin::new(s).poll_close(cx),
+            InnerAsyncNetworkStream::None => {
+                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
+                Poll::Ready(Ok(()))
+            }
+        }
+    }
+}

src/transport/smtp/client/connection.rs

@@ -0,0 +1,292 @@
+use std::{
+    fmt::Display,
+    io::{self, BufRead, BufReader, Write},
+    net::ToSocketAddrs,
+    time::Duration,
+};
+
+use super::{ClientCodec, NetworkStream, TlsParameters};
+use crate::{
+    address::Envelope,
+    transport::smtp::{
+        authentication::{Credentials, Mechanism},
+        commands::*,
+        error::Error,
+        extension::{ClientId, Extension, MailBodyParameter, MailParameter, ServerInfo},
+        response::{parse_response, Response},
+    },
+};
+
+#[cfg(feature = "tracing")]
+use super::escape_crlf;
+
+macro_rules! try_smtp (
+    ($err: expr, $client: ident) => ({
+        match $err {
+            Ok(val) => val,
+            Err(err) => {
+                $client.abort();
+                return Err(From::from(err))
+            },
+        }
+    })
+);
+
+/// Structure that implements the SMTP client
+pub struct SmtpConnection {
+    /// TCP stream between client and server
+    /// Value is None before connection
+    stream: BufReader<NetworkStream>,
+    /// Panic state
+    panic: bool,
+    /// Information about the server
+    server_info: ServerInfo,
+}
+
+impl SmtpConnection {
+    pub fn server_info(&self) -> &ServerInfo {
+        &self.server_info
+    }
+
+    // FIXME add simple connect and rename this one
+
+    /// Connects to the configured server
+    ///
+    /// Sends EHLO and parses server information
+    pub fn connect<A: ToSocketAddrs>(
+        server: A,
+        timeout: Option<Duration>,
+        hello_name: &ClientId,
+        tls_parameters: Option<&TlsParameters>,
+    ) -> Result<SmtpConnection, Error> {
+        let stream = NetworkStream::connect(server, timeout, tls_parameters)?;
+        let stream = BufReader::new(stream);
+        let mut conn = SmtpConnection {
+            stream,
+            panic: false,
+            server_info: ServerInfo::default(),
+        };
+        conn.set_timeout(timeout)?;
+        // TODO log
+        let _response = conn.read_response()?;
+
+        conn.ehlo(hello_name)?;
+
+        // Print server information
+        #[cfg(feature = "tracing")]
+        tracing::debug!("server {}", conn.server_info);
+        Ok(conn)
+    }
+
+    pub fn send(&mut self, envelope: &Envelope, email: &[u8]) -> Result<Response, Error> {
+        // Mail
+        let mut mail_options = vec![];
+
+        // Internationalization handling
+        //
+        // * 8BITMIME: https://tools.ietf.org/html/rfc6152
+        // * SMTPUTF8: https://tools.ietf.org/html/rfc653
+
+        // Check for non-ascii addresses and use the SMTPUTF8 option if any.
+        if envelope.has_non_ascii_addresses() {
+            if !self.server_info().supports_feature(Extension::SmtpUtfEight) {
+                // don't try to send non-ascii addresses (per RFC)
+                return Err(Error::Client(
+                    "Envelope contains non-ascii chars but server does not support SMTPUTF8",
+                ));
+            }
+            mail_options.push(MailParameter::SmtpUtfEight);
+        }
+
+        // Check for non-ascii content in message
+        if !email.is_ascii() {
+            if !self.server_info().supports_feature(Extension::EightBitMime) {
+                return Err(Error::Client(
+                    "Message contains non-ascii chars but server does not support 8BITMIME",
+                ));
+            }
+            mail_options.push(MailParameter::Body(MailBodyParameter::EightBitMime));
+        }
+
+        try_smtp!(
+            self.command(Mail::new(envelope.from().cloned(), mail_options)),
+            self
+        );
+
+        // Recipient
+        for to_address in envelope.to() {
+            try_smtp!(self.command(Rcpt::new(to_address.clone(), vec![])), self);
+        }
+
+        // Data
+        try_smtp!(self.command(Data), self);
+
+        // Message content
+        let result = try_smtp!(self.message(email), self);
+        Ok(result)
+    }
+
+    pub fn has_broken(&self) -> bool {
+        self.panic
+    }
+
+    pub fn can_starttls(&self) -> bool {
+        !self.is_encrypted() && self.server_info.supports_feature(Extension::StartTls)
+    }
+
+    #[allow(unused_variables)]
+    pub fn starttls(
+        &mut self,
+        tls_parameters: &TlsParameters,
+        hello_name: &ClientId,
+    ) -> Result<(), Error> {
+        if self.server_info.supports_feature(Extension::StartTls) {
+            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+            {
+                try_smtp!(self.command(Starttls), self);
+                try_smtp!(self.stream.get_mut().upgrade_tls(tls_parameters), self);
+                #[cfg(feature = "tracing")]
+                tracing::debug!("connection encrypted");
+                // Send EHLO again
+                try_smtp!(self.ehlo(hello_name), self);
+                Ok(())
+            }
+            #[cfg(not(any(feature = "native-tls", feature = "rustls-tls")))]
+            // This should never happen as `Tls` can only be created
+            // when a TLS library is enabled
+            unreachable!("TLS support required but not supported");
+        } else {
+            Err(Error::Client("STARTTLS is not supported on this server"))
+        }
+    }
+
+    /// Send EHLO and update server info
+    fn ehlo(&mut self, hello_name: &ClientId) -> Result<(), Error> {
+        let ehlo_response = try_smtp!(self.command(Ehlo::new(hello_name.clone())), self);
+        self.server_info = try_smtp!(ServerInfo::from_response(&ehlo_response), self);
+        Ok(())
+    }
+
+    pub fn quit(&mut self) -> Result<Response, Error> {
+        Ok(try_smtp!(self.command(Quit), self))
+    }
+
+    pub fn abort(&mut self) {
+        // Only try to quit if we are not already broken
+        if !self.panic {
+            self.panic = true;
+            let _ = self.command(Quit);
+        }
+    }
+
+    /// Sets the underlying stream
+    pub fn set_stream(&mut self, stream: NetworkStream) {
+        self.stream = BufReader::new(stream);
+    }
+
+    /// Tells if the underlying stream is currently encrypted
+    pub fn is_encrypted(&self) -> bool {
+        self.stream.get_ref().is_encrypted()
+    }
+
+    /// Set timeout
+    pub fn set_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
+        self.stream.get_mut().set_read_timeout(duration)?;
+        self.stream.get_mut().set_write_timeout(duration)
+    }
+
+    /// Checks if the server is connected using the NOOP SMTP command
+    pub fn test_connected(&mut self) -> bool {
+        self.command(Noop).is_ok()
+    }
+
+    /// Sends an AUTH command with the given mechanism, and handles challenge if needed
+    pub fn auth(
+        &mut self,
+        mechanisms: &[Mechanism],
+        credentials: &Credentials,
+    ) -> Result<Response, Error> {
+        let mechanism = self
+            .server_info
+            .get_auth_mechanism(mechanisms)
+            .ok_or(Error::Client(
+                "No compatible authentication mechanism was found",
+            ))?;
+
+        // Limit challenges to avoid blocking
+        let mut challenges = 10;
+        let mut response = self.command(Auth::new(mechanism, credentials.clone(), None)?)?;
+
+        while challenges > 0 && response.has_code(334) {
+            challenges -= 1;
+            response = try_smtp!(
+                self.command(Auth::new_from_response(
+                    mechanism,
+                    credentials.clone(),
+                    &response,
+                )?),
+                self
+            );
+        }
+
+        if challenges == 0 {
+            Err(Error::ResponseParsing("Unexpected number of challenges"))
+        } else {
+            Ok(response)
+        }
+    }
+
+    /// Sends the message content
+    pub fn message(&mut self, message: &[u8]) -> Result<Response, Error> {
+        let mut out_buf: Vec<u8> = vec![];
+        let mut codec = ClientCodec::new();
+        codec.encode(message, &mut out_buf);
+        self.write(out_buf.as_slice())?;
+        self.write(b"\r\n.\r\n")?;
+        self.read_response()
+    }
+
+    /// Sends an SMTP command
+    pub fn command<C: Display>(&mut self, command: C) -> Result<Response, Error> {
+        self.write(command.to_string().as_bytes())?;
+        self.read_response()
+    }
+
+    /// Writes a string to the server
+    fn write(&mut self, string: &[u8]) -> Result<(), Error> {
+        self.stream.get_mut().write_all(string)?;
+        self.stream.get_mut().flush()?;
+
+        #[cfg(feature = "tracing")]
+        tracing::debug!("Wrote: {}", escape_crlf(&String::from_utf8_lossy(string)));
+        Ok(())
+    }
+
+    /// Gets the SMTP response
+    pub fn read_response(&mut self) -> Result<Response, Error> {
+        let mut buffer = String::with_capacity(100);
+
+        while self.stream.read_line(&mut buffer)? > 0 {
+            #[cfg(feature = "tracing")]
+            tracing::debug!("<< {}", escape_crlf(&buffer));
+            match parse_response(&buffer) {
+                Ok((_remaining, response)) => {
+                    if response.is_positive() {
+                        return Ok(response);
+                    }
+
+                    return Err(response.into());
+                }
+                Err(nom::Err::Failure(e)) => {
+                    return Err(Error::Parsing(e.code));
+                }
+                Err(nom::Err::Incomplete(_)) => { /* read more */ }
+                Err(nom::Err::Error(e)) => {
+                    return Err(Error::Parsing(e.code));
+                }
+            }
+        }
+
+        Err(io::Error::new(io::ErrorKind::Other, "incomplete").into())
+    }
+}

src/transport/smtp/client/mock.rs

@@ -1,8 +1,10 @@
 #![allow(missing_docs)]
 // Comes from https://github.com/inre/rust-mq/blob/master/netopt
 
-use std::io::{self, Cursor, Read, Write};
-use std::sync::{Arc, Mutex};
+use std::{
+    io::{self, Cursor, Read, Write},
+    sync::{Arc, Mutex},
+};
 
 pub type MockCursor = Cursor<Vec<u8>>;
 
@@ -88,7 +90,7 @@ mod test {
     fn write_take_test() {
         let mut mock = MockStream::new();
         // write to mock stream
-        mock.write(&[1, 2, 3]).unwrap();
+        mock.write_all(&[1, 2, 3]).unwrap();
         assert_eq!(mock.take_vec(), vec![1, 2, 3]);
     }
 
@@ -104,7 +106,7 @@ mod test {
     fn clone_test() {
         let mut mock = MockStream::new();
         let mut cloned = mock.clone();
-        mock.write(&[6, 7]).unwrap();
+        mock.write_all(&[6, 7]).unwrap();
         assert_eq!(cloned.take_vec(), vec![6, 7]);
     }
 
@@ -112,7 +114,7 @@ mod test {
     fn swap_test() {
         let mut mock = MockStream::new();
         let mut vec = Vec::new();
-        mock.write(&[8, 9, 10]).unwrap();
+        mock.write_all(&[8, 9, 10]).unwrap();
         mock.swap();
         mock.read_to_end(&mut vec).unwrap();
         assert_eq!(vec, vec![8, 9, 10]);

src/transport/smtp/client/mod.rs

@@ -0,0 +1,140 @@
+//! SMTP client
+//!
+//! `SmtpConnection` allows manually sending SMTP commands.
+//!
+//! ```rust,no_run
+//! # use std::error::Error;
+//!
+//! # #[cfg(feature = "smtp-transport")]
+//! # fn main() -> Result<(), Box<dyn Error>> {
+//! use lettre::transport::smtp::{SMTP_PORT, extension::ClientId, commands::*, client::SmtpConnection};
+//!
+//! let hello = ClientId::Domain("my_hostname".to_string());
+//! let mut client = SmtpConnection::connect(&("localhost", SMTP_PORT), None, &hello, None)?;
+//! client.command(
+//!         Mail::new(Some("user@example.com".parse()?), vec![])
+//!     )?;
+//! client.command(
+//!         Rcpt::new("user@example.org".parse()?, vec![])
+//!       )?;
+//! client.command(Data)?;
+//! client.message("Test email".as_bytes())?;
+//! client.command(Quit)?;
+//! # Ok(())
+//! # }
+//! ```
+
+#[cfg(feature = "serde")]
+use std::fmt::Debug;
+
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+pub(crate) use self::async_connection::AsyncSmtpConnection;
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+pub(crate) use self::async_net::AsyncNetworkStream;
+use self::net::NetworkStream;
+#[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+pub(super) use self::tls::InnerTlsParameters;
+pub use self::{
+    connection::SmtpConnection,
+    mock::MockStream,
+    tls::{Certificate, Tls, TlsParameters, TlsParametersBuilder},
+};
+
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+mod async_connection;
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+mod async_net;
+mod connection;
+mod mock;
+mod net;
+mod tls;
+
+/// The codec used for transparency
+#[derive(Default, Clone, Copy, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+struct ClientCodec {
+    escape_count: u8,
+}
+
+impl ClientCodec {
+    /// Creates a new client codec
+    pub fn new() -> Self {
+        ClientCodec::default()
+    }
+
+    /// Adds transparency
+    fn encode(&mut self, frame: &[u8], buf: &mut Vec<u8>) {
+        match frame.len() {
+            0 => {
+                match self.escape_count {
+                    0 => buf.extend_from_slice(b"\r\n.\r\n"),
+                    1 => buf.extend_from_slice(b"\n.\r\n"),
+                    2 => buf.extend_from_slice(b".\r\n"),
+                    _ => unreachable!(),
+                }
+                self.escape_count = 0;
+            }
+            _ => {
+                let mut start = 0;
+                for (idx, byte) in frame.iter().enumerate() {
+                    match self.escape_count {
+                        0 => self.escape_count = if *byte == b'\r' { 1 } else { 0 },
+                        1 => self.escape_count = if *byte == b'\n' { 2 } else { 0 },
+                        2 => self.escape_count = if *byte == b'.' { 3 } else { 0 },
+                        _ => unreachable!(),
+                    }
+                    if self.escape_count == 3 {
+                        self.escape_count = 0;
+                        buf.extend_from_slice(&frame[start..idx]);
+                        buf.extend_from_slice(b".");
+                        start = idx;
+                    }
+                }
+                buf.extend_from_slice(&frame[start..]);
+            }
+        }
+    }
+}
+
+/// Returns the string replacing all the CRLF with "\<CRLF\>"
+/// Used for debug displays
+#[cfg(feature = "tracing")]
+pub(super) fn escape_crlf(string: &str) -> String {
+    string.replace("\r\n", "<CRLF>")
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_codec() {
+        let mut codec = ClientCodec::new();
+        let mut buf: Vec<u8> = vec![];
+
+        codec.encode(b"test\r\n", &mut buf);
+        codec.encode(b".\r\n", &mut buf);
+        codec.encode(b"\r\ntest", &mut buf);
+        codec.encode(b"te\r\n.\r\nst", &mut buf);
+        codec.encode(b"test", &mut buf);
+        codec.encode(b"test.", &mut buf);
+        codec.encode(b"test\n", &mut buf);
+        codec.encode(b".test\n", &mut buf);
+        codec.encode(b"test", &mut buf);
+        assert_eq!(
+            String::from_utf8(buf).unwrap(),
+            "test\r\n..\r\n\r\ntestte\r\n..\r\nsttesttest.test\n.test\ntest"
+        );
+    }
+
+    #[test]
+    #[cfg(feature = "log")]
+    fn test_escape_crlf() {
+        assert_eq!(escape_crlf("\r\n"), "<CRLF>");
+        assert_eq!(escape_crlf("EHLO my_name\r\n"), "EHLO my_name<CRLF>");
+        assert_eq!(
+            escape_crlf("EHLO my_name\r\nSIZE 42\r\n"),
+            "EHLO my_name<CRLF>SIZE 42<CRLF>"
+        );
+    }
+}

src/transport/smtp/client/net.rs

@@ -0,0 +1,240 @@
+#[cfg(feature = "rustls-tls")]
+use std::sync::Arc;
+use std::{
+    io::{self, Read, Write},
+    net::{Ipv4Addr, Shutdown, SocketAddr, SocketAddrV4, TcpStream, ToSocketAddrs},
+    time::Duration,
+};
+
+#[cfg(feature = "native-tls")]
+use native_tls::TlsStream;
+
+#[cfg(feature = "rustls-tls")]
+use rustls::{ClientSession, StreamOwned};
+
+#[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+use super::InnerTlsParameters;
+use super::{MockStream, TlsParameters};
+use crate::transport::smtp::Error;
+
+/// A network stream
+pub struct NetworkStream {
+    inner: InnerNetworkStream,
+}
+
+/// Represents the different types of underlying network streams
+// usually only one TLS backend at a time is going to be enabled,
+// so clippy::large_enum_variant doesn't make sense here
+#[allow(clippy::large_enum_variant)]
+enum InnerNetworkStream {
+    /// Plain TCP stream
+    Tcp(TcpStream),
+    /// Encrypted TCP stream
+    #[cfg(feature = "native-tls")]
+    NativeTls(TlsStream<TcpStream>),
+    /// Encrypted TCP stream
+    #[cfg(feature = "rustls-tls")]
+    RustlsTls(StreamOwned<ClientSession, TcpStream>),
+    /// Mock stream
+    Mock(MockStream),
+}
+
+impl NetworkStream {
+    fn new(inner: InnerNetworkStream) -> Self {
+        NetworkStream { inner }
+    }
+
+    pub fn new_mock(mock: MockStream) -> Self {
+        Self::new(InnerNetworkStream::Mock(mock))
+    }
+
+    /// Returns peer's address
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref s) => s.peer_addr(),
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref s) => s.get_ref().peer_addr(),
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref s) => s.get_ref().peer_addr(),
+            InnerNetworkStream::Mock(_) => Ok(SocketAddr::V4(SocketAddrV4::new(
+                Ipv4Addr::new(127, 0, 0, 1),
+                80,
+            ))),
+        }
+    }
+
+    /// Shutdowns the connection
+    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref s) => s.shutdown(how),
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref s) => s.get_ref().shutdown(how),
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref s) => s.get_ref().shutdown(how),
+            InnerNetworkStream::Mock(_) => Ok(()),
+        }
+    }
+
+    pub fn connect<T: ToSocketAddrs>(
+        server: T,
+        timeout: Option<Duration>,
+        tls_parameters: Option<&TlsParameters>,
+    ) -> Result<NetworkStream, Error> {
+        fn try_connect_timeout<T: ToSocketAddrs>(
+            server: T,
+            timeout: Duration,
+        ) -> Result<TcpStream, Error> {
+            let addrs = server.to_socket_addrs()?;
+            for addr in addrs {
+                if let Ok(result) = TcpStream::connect_timeout(&addr, timeout) {
+                    return Ok(result);
+                }
+            }
+            Err(Error::Client("Could not connect"))
+        }
+
+        let tcp_stream = match timeout {
+            Some(t) => try_connect_timeout(server, t)?,
+            None => TcpStream::connect(server)?,
+        };
+
+        let mut stream = NetworkStream::new(InnerNetworkStream::Tcp(tcp_stream));
+        if let Some(tls_parameters) = tls_parameters {
+            stream.upgrade_tls(tls_parameters)?;
+        }
+        Ok(stream)
+    }
+
+    pub fn upgrade_tls(&mut self, tls_parameters: &TlsParameters) -> Result<(), Error> {
+        match &self.inner {
+            #[cfg(not(any(feature = "native-tls", feature = "rustls-tls")))]
+            InnerNetworkStream::Tcp(_) => {
+                let _ = tls_parameters;
+                panic!("Trying to upgrade an NetworkStream without having enabled either the native-tls or the rustls-tls feature");
+            }
+
+            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+            InnerNetworkStream::Tcp(_) => {
+                // get owned TcpStream
+                let tcp_stream =
+                    std::mem::replace(&mut self.inner, InnerNetworkStream::Mock(MockStream::new()));
+                let tcp_stream = match tcp_stream {
+                    InnerNetworkStream::Tcp(tcp_stream) => tcp_stream,
+                    _ => unreachable!(),
+                };
+
+                self.inner = Self::upgrade_tls_impl(tcp_stream, tls_parameters)?;
+                Ok(())
+            }
+            _ => Ok(()),
+        }
+    }
+
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    fn upgrade_tls_impl(
+        tcp_stream: TcpStream,
+        tls_parameters: &TlsParameters,
+    ) -> Result<InnerNetworkStream, Error> {
+        Ok(match &tls_parameters.connector {
+            #[cfg(feature = "native-tls")]
+            InnerTlsParameters::NativeTls(connector) => {
+                let stream = connector
+                    .connect(tls_parameters.domain(), tcp_stream)
+                    .map_err(|err| Error::Io(io::Error::new(io::ErrorKind::Other, err)))?;
+                InnerNetworkStream::NativeTls(stream)
+            }
+            #[cfg(feature = "rustls-tls")]
+            InnerTlsParameters::RustlsTls(connector) => {
+                use webpki::DNSNameRef;
+
+                let domain = DNSNameRef::try_from_ascii_str(tls_parameters.domain())?;
+                let stream = StreamOwned::new(
+                    ClientSession::new(&Arc::new(connector.clone()), domain),
+                    tcp_stream,
+                );
+
+                InnerNetworkStream::RustlsTls(stream)
+            }
+        })
+    }
+
+    pub fn is_encrypted(&self) -> bool {
+        match self.inner {
+            InnerNetworkStream::Tcp(_) | InnerNetworkStream::Mock(_) => false,
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(_) => true,
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(_) => true,
+        }
+    }
+
+    pub fn set_read_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref mut stream) => stream.set_read_timeout(duration),
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref mut stream) => {
+                stream.get_ref().set_read_timeout(duration)
+            }
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref mut stream) => {
+                stream.get_ref().set_read_timeout(duration)
+            }
+            InnerNetworkStream::Mock(_) => Ok(()),
+        }
+    }
+
+    /// Set write timeout for IO calls
+    pub fn set_write_timeout(&mut self, duration: Option<Duration>) -> io::Result<()> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref mut stream) => stream.set_write_timeout(duration),
+
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref mut stream) => {
+                stream.get_ref().set_write_timeout(duration)
+            }
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref mut stream) => {
+                stream.get_ref().set_write_timeout(duration)
+            }
+
+            InnerNetworkStream::Mock(_) => Ok(()),
+        }
+    }
+}
+
+impl Read for NetworkStream {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref mut s) => s.read(buf),
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref mut s) => s.read(buf),
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref mut s) => s.read(buf),
+            InnerNetworkStream::Mock(ref mut s) => s.read(buf),
+        }
+    }
+}
+
+impl Write for NetworkStream {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref mut s) => s.write(buf),
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref mut s) => s.write(buf),
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref mut s) => s.write(buf),
+            InnerNetworkStream::Mock(ref mut s) => s.write(buf),
+        }
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        match self.inner {
+            InnerNetworkStream::Tcp(ref mut s) => s.flush(),
+            #[cfg(feature = "native-tls")]
+            InnerNetworkStream::NativeTls(ref mut s) => s.flush(),
+            #[cfg(feature = "rustls-tls")]
+            InnerNetworkStream::RustlsTls(ref mut s) => s.flush(),
+            InnerNetworkStream::Mock(ref mut s) => s.flush(),
+        }
+    }
+}

src/transport/smtp/client/tls.rs

@@ -0,0 +1,283 @@
+#[cfg(feature = "rustls-tls")]
+use std::sync::Arc;
+
+#[cfg(feature = "native-tls")]
+use native_tls::{Protocol, TlsConnector};
+#[cfg(feature = "rustls-tls")]
+use rustls::{ClientConfig, RootCertStore, ServerCertVerified, ServerCertVerifier, TLSError};
+#[cfg(feature = "rustls-tls")]
+use webpki::DNSNameRef;
+
+use crate::transport::smtp::error::Error;
+
+/// Accepted protocols by default.
+/// This removes TLS 1.0 and 1.1 compared to tls-native defaults.
+// This is also rustls' default behavior
+#[cfg(feature = "native-tls")]
+const DEFAULT_TLS_MIN_PROTOCOL: Protocol = Protocol::Tlsv12;
+
+/// How to apply TLS to a client connection
+#[derive(Clone)]
+#[allow(missing_copy_implementations)]
+pub enum Tls {
+    /// Insecure connection only (for testing purposes)
+    None,
+    /// Start with insecure connection and use `STARTTLS` when available
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    Opportunistic(TlsParameters),
+    /// Start with insecure connection and require `STARTTLS`
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    Required(TlsParameters),
+    /// Use TLS wrapped connection
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    Wrapper(TlsParameters),
+}
+
+/// Parameters to use for secure clients
+#[derive(Clone)]
+#[allow(missing_debug_implementations)]
+pub struct TlsParameters {
+    pub(crate) connector: InnerTlsParameters,
+    /// The domain name which is expected in the TLS certificate from the server
+    pub(super) domain: String,
+}
+
+/// Builder for `TlsParameters`
+#[derive(Clone)]
+pub struct TlsParametersBuilder {
+    domain: String,
+    root_certs: Vec<Certificate>,
+    accept_invalid_hostnames: bool,
+    accept_invalid_certs: bool,
+}
+
+impl TlsParametersBuilder {
+    /// Creates a new builder for `TlsParameters`
+    pub fn new(domain: String) -> Self {
+        Self {
+            domain,
+            root_certs: Vec::new(),
+            accept_invalid_hostnames: false,
+            accept_invalid_certs: false,
+        }
+    }
+
+    /// Add a custom root certificate
+    ///
+    /// Can be used to safely connect to a server using a self signed certificate, for example.
+    pub fn add_root_certificate(mut self, cert: Certificate) -> Self {
+        self.root_certs.push(cert);
+        self
+    }
+
+    /// Controls whether certificates with an invalid hostname are accepted
+    ///
+    /// Defaults to `false`.
+    ///
+    /// # Warning
+    ///
+    /// You should think very carefully before using this method.
+    /// If hostname verification is disabled *any* valid certificate,
+    /// including those from other sites, are trusted.
+    ///
+    /// This method introduces significant vulnerabilities to man-in-the-middle attacks.
+    ///
+    /// Hostname verification can only be disabled with the `native-tls` TLS backend.
+    #[cfg(feature = "native-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+    pub fn dangerous_accept_invalid_hostnames(mut self, accept_invalid_hostnames: bool) -> Self {
+        self.accept_invalid_hostnames = accept_invalid_hostnames;
+        self
+    }
+
+    /// Controls whether invalid certificates are accepted
+    ///
+    /// Defaults to `false`.
+    ///
+    /// # Warning
+    ///
+    /// You should think very carefully before using this method.
+    /// If certificate verification is disabled, *any* certificate
+    /// is trusted for use, including:
+    ///
+    /// * Self signed certificates
+    /// * Certificates from different hostnames
+    /// * Expired certificates
+    ///
+    /// This method should only be used as a last resort, as it introduces
+    /// significant vulnerabilities to man-in-the-middle attacks.
+    pub fn dangerous_accept_invalid_certs(mut self, accept_invalid_certs: bool) -> Self {
+        self.accept_invalid_certs = accept_invalid_certs;
+        self
+    }
+
+    /// Creates a new `TlsParameters` using native-tls or rustls
+    /// depending on which one is available
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
+    // TODO: remove below line once native-tls is supported with async-std
+    #[allow(unreachable_code)]
+    pub fn build(self) -> Result<TlsParameters, Error> {
+        // TODO: remove once native-tls is supported with async-std
+        #[cfg(all(feature = "rustls-tls", feature = "async-std1"))]
+        return self.build_rustls();
+
+        #[cfg(feature = "native-tls")]
+        return self.build_native();
+
+        #[cfg(not(feature = "native-tls"))]
+        return self.build_rustls();
+    }
+
+    /// Creates a new `TlsParameters` using native-tls with the provided configuration
+    #[cfg(feature = "native-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+    pub fn build_native(self) -> Result<TlsParameters, Error> {
+        let mut tls_builder = TlsConnector::builder();
+
+        for cert in self.root_certs {
+            tls_builder.add_root_certificate(cert.native_tls);
+        }
+        tls_builder.danger_accept_invalid_hostnames(self.accept_invalid_hostnames);
+        tls_builder.danger_accept_invalid_certs(self.accept_invalid_certs);
+
+        tls_builder.min_protocol_version(Some(DEFAULT_TLS_MIN_PROTOCOL));
+        let connector = tls_builder.build()?;
+        Ok(TlsParameters {
+            connector: InnerTlsParameters::NativeTls(connector),
+            domain: self.domain,
+        })
+    }
+
+    /// Creates a new `TlsParameters` using rustls with the provided configuration
+    #[cfg(feature = "rustls-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
+    pub fn build_rustls(self) -> Result<TlsParameters, Error> {
+        use webpki_roots::TLS_SERVER_ROOTS;
+
+        let mut tls = ClientConfig::new();
+
+        for cert in self.root_certs {
+            for rustls_cert in cert.rustls {
+                tls.root_store
+                    .add(&rustls_cert)
+                    .map_err(|_| Error::InvalidCertificate)?;
+            }
+        }
+        if self.accept_invalid_certs {
+            tls.dangerous()
+                .set_certificate_verifier(Arc::new(InvalidCertsVerifier {}));
+        }
+
+        tls.root_store.add_server_trust_anchors(&TLS_SERVER_ROOTS);
+        Ok(TlsParameters {
+            connector: InnerTlsParameters::RustlsTls(tls),
+            domain: self.domain,
+        })
+    }
+}
+
+#[derive(Clone)]
+pub enum InnerTlsParameters {
+    #[cfg(feature = "native-tls")]
+    NativeTls(TlsConnector),
+    #[cfg(feature = "rustls-tls")]
+    RustlsTls(ClientConfig),
+}
+
+impl TlsParameters {
+    /// Creates a new `TlsParameters` using native-tls or rustls
+    /// depending on which one is available
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
+    pub fn new(domain: String) -> Result<Self, Error> {
+        TlsParametersBuilder::new(domain).build()
+    }
+
+    pub fn builder(domain: String) -> TlsParametersBuilder {
+        TlsParametersBuilder::new(domain)
+    }
+
+    /// Creates a new `TlsParameters` using native-tls
+    #[cfg(feature = "native-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+    pub fn new_native(domain: String) -> Result<Self, Error> {
+        TlsParametersBuilder::new(domain).build_native()
+    }
+
+    /// Creates a new `TlsParameters` using rustls
+    #[cfg(feature = "rustls-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
+    pub fn new_rustls(domain: String) -> Result<Self, Error> {
+        TlsParametersBuilder::new(domain).build_rustls()
+    }
+
+    pub fn domain(&self) -> &str {
+        &self.domain
+    }
+}
+
+/// A client certificate that can be used with [`TlsParametersBuilder::add_root_certificate`]
+#[derive(Clone)]
+#[allow(missing_copy_implementations)]
+pub struct Certificate {
+    #[cfg(feature = "native-tls")]
+    native_tls: native_tls::Certificate,
+    #[cfg(feature = "rustls-tls")]
+    rustls: Vec<rustls::Certificate>,
+}
+
+impl Certificate {
+    /// Create a `Certificate` from a DER encoded certificate
+    pub fn from_der(der: Vec<u8>) -> Result<Self, Error> {
+        #[cfg(feature = "native-tls")]
+        let native_tls_cert =
+            native_tls::Certificate::from_der(&der).map_err(|_| Error::InvalidCertificate)?;
+
+        Ok(Self {
+            #[cfg(feature = "native-tls")]
+            native_tls: native_tls_cert,
+            #[cfg(feature = "rustls-tls")]
+            rustls: vec![rustls::Certificate(der)],
+        })
+    }
+
+    /// Create a `Certificate` from a PEM encoded certificate
+    pub fn from_pem(pem: &[u8]) -> Result<Self, Error> {
+        #[cfg(feature = "native-tls")]
+        let native_tls_cert =
+            native_tls::Certificate::from_pem(pem).map_err(|_| Error::InvalidCertificate)?;
+
+        #[cfg(feature = "rustls-tls")]
+        let rustls_cert = {
+            use rustls::internal::pemfile;
+            use std::io::Cursor;
+
+            let mut pem = Cursor::new(pem);
+            pemfile::certs(&mut pem).map_err(|_| Error::InvalidCertificate)?
+        };
+
+        Ok(Self {
+            #[cfg(feature = "native-tls")]
+            native_tls: native_tls_cert,
+            #[cfg(feature = "rustls-tls")]
+            rustls: rustls_cert,
+        })
+    }
+}
+
+#[cfg(feature = "rustls-tls")]
+struct InvalidCertsVerifier;
+
+#[cfg(feature = "rustls-tls")]
+impl ServerCertVerifier for InvalidCertsVerifier {
+    fn verify_server_cert(
+        &self,
+        _roots: &RootCertStore,
+        _presented_certs: &[rustls::Certificate],
+        _dns_name: DNSNameRef<'_>,
+        _ocsp_response: &[u8],
+    ) -> Result<ServerCertVerified, TLSError> {
+        Ok(ServerCertVerified::assertion())
+    }
+}

src/transport/smtp/commands.rs

@@ -1,61 +1,61 @@
-#![cfg_attr(feature = "cargo-clippy", allow(clippy::write_with_newline))]
-
 //! SMTP commands
 
-use base64;
-use smtp::authentication::{Credentials, Mechanism};
-use smtp::error::Error;
-use smtp::extension::ClientId;
-use smtp::extension::{MailParameter, RcptParameter};
-use smtp::response::Response;
+use crate::{
+    transport::smtp::{
+        authentication::{Credentials, Mechanism},
+        error::Error,
+        extension::{ClientId, MailParameter, RcptParameter},
+        response::Response,
+    },
+    Address,
+};
 use std::fmt::{self, Display, Formatter};
-use EmailAddress;
 
 /// EHLO command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct EhloCommand {
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Ehlo {
     client_id: ClientId,
 }
 
-impl Display for EhloCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Ehlo {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(f, "EHLO {}\r\n", self.client_id)
     }
 }
 
-impl EhloCommand {
+impl Ehlo {
     /// Creates a EHLO command
-    pub fn new(client_id: ClientId) -> EhloCommand {
-        EhloCommand { client_id }
+    pub fn new(client_id: ClientId) -> Ehlo {
+        Ehlo { client_id }
     }
 }
 
 /// STARTTLS command
 #[derive(PartialEq, Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct StarttlsCommand;
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Starttls;
 
-impl Display for StarttlsCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Starttls {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.write_str("STARTTLS\r\n")
     }
 }
 
 /// MAIL command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct MailCommand {
-    sender: Option<EmailAddress>,
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Mail {
+    sender: Option<Address>,
     parameters: Vec<MailParameter>,
 }
 
-impl Display for MailCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Mail {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(
             f,
             "MAIL FROM:<{}>",
-            self.sender.as_ref().map(|x| x.as_ref()).unwrap_or("")
+            self.sender.as_ref().map(|s| s.as_ref()).unwrap_or("")
         )?;
         for parameter in &self.parameters {
             write!(f, " {}", parameter)?;
@@ -64,23 +64,23 @@ impl Display for MailCommand {
     }
 }
 
-impl MailCommand {
+impl Mail {
     /// Creates a MAIL command
-    pub fn new(sender: Option<EmailAddress>, parameters: Vec<MailParameter>) -> MailCommand {
-        MailCommand { sender, parameters }
+    pub fn new(sender: Option<Address>, parameters: Vec<MailParameter>) -> Mail {
+        Mail { sender, parameters }
     }
 }
 
 /// RCPT command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct RcptCommand {
-    recipient: EmailAddress,
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Rcpt {
+    recipient: Address,
     parameters: Vec<RcptParameter>,
 }
 
-impl Display for RcptCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Rcpt {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(f, "RCPT TO:<{}>", self.recipient)?;
         for parameter in &self.parameters {
             write!(f, " {}", parameter)?;
@@ -89,10 +89,10 @@ impl Display for RcptCommand {
     }
 }
 
-impl RcptCommand {
+impl Rcpt {
     /// Creates an RCPT command
-    pub fn new(recipient: EmailAddress, parameters: Vec<RcptParameter>) -> RcptCommand {
-        RcptCommand {
+    pub fn new(recipient: Address, parameters: Vec<RcptParameter>) -> Rcpt {
+        Rcpt {
             recipient,
             parameters,
         }
@@ -101,129 +101,125 @@ impl RcptCommand {
 
 /// DATA command
 #[derive(PartialEq, Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct DataCommand;
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Data;
 
-impl Display for DataCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Data {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.write_str("DATA\r\n")
     }
 }
 
 /// QUIT command
 #[derive(PartialEq, Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct QuitCommand;
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Quit;
 
-impl Display for QuitCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Quit {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.write_str("QUIT\r\n")
     }
 }
 
 /// NOOP command
 #[derive(PartialEq, Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct NoopCommand;
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Noop;
 
-impl Display for NoopCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Noop {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.write_str("NOOP\r\n")
     }
 }
 
 /// HELP command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct HelpCommand {
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Help {
     argument: Option<String>,
 }
 
-impl Display for HelpCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Help {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.write_str("HELP")?;
-        if self.argument.is_some() {
-            write!(f, " {}", self.argument.as_ref().unwrap())?;
+        if let Some(argument) = &self.argument {
+            write!(f, " {}", argument)?;
         }
         f.write_str("\r\n")
     }
 }
 
-impl HelpCommand {
+impl Help {
     /// Creates an HELP command
-    pub fn new(argument: Option<String>) -> HelpCommand {
-        HelpCommand { argument }
+    pub fn new(argument: Option<String>) -> Help {
+        Help { argument }
     }
 }
 
 /// VRFY command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct VrfyCommand {
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Vrfy {
     argument: String,
 }
 
-impl Display for VrfyCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        #[cfg_attr(feature = "cargo-clippy", allow(clippy::write_with_newline))]
+impl Display for Vrfy {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(f, "VRFY {}\r\n", self.argument)
     }
 }
 
-impl VrfyCommand {
+impl Vrfy {
     /// Creates a VRFY command
-    pub fn new(argument: String) -> VrfyCommand {
-        VrfyCommand { argument }
+    pub fn new(argument: String) -> Vrfy {
+        Vrfy { argument }
     }
 }
 
 /// EXPN command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct ExpnCommand {
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Expn {
     argument: String,
 }
 
-impl Display for ExpnCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Expn {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(f, "EXPN {}\r\n", self.argument)
     }
 }
 
-impl ExpnCommand {
+impl Expn {
     /// Creates an EXPN command
-    pub fn new(argument: String) -> ExpnCommand {
-        ExpnCommand { argument }
+    pub fn new(argument: String) -> Expn {
+        Expn { argument }
     }
 }
 
 /// RSET command
 #[derive(PartialEq, Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct RsetCommand;
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Rset;
 
-impl Display for RsetCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+impl Display for Rset {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.write_str("RSET\r\n")
     }
 }
 
 /// AUTH command
 #[derive(PartialEq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
-pub struct AuthCommand {
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Auth {
     mechanism: Mechanism,
     credentials: Credentials,
     challenge: Option<String>,
     response: Option<String>,
 }
 
-impl Display for AuthCommand {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        let encoded_response = self
-            .response
-            .as_ref()
-            .map(|r| base64::encode_config(r.as_bytes(), base64::STANDARD));
+impl Display for Auth {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let encoded_response = self.response.as_ref().map(base64::encode);
 
         if self.mechanism.supports_initial_response() {
             write!(f, "AUTH {} {}", self.mechanism, encoded_response.unwrap())?;
@@ -237,19 +233,19 @@ impl Display for AuthCommand {
     }
 }
 
-impl AuthCommand {
+impl Auth {
     /// Creates an AUTH command (from a challenge if provided)
     pub fn new(
         mechanism: Mechanism,
         credentials: Credentials,
         challenge: Option<String>,
-    ) -> Result<AuthCommand, Error> {
+    ) -> Result<Auth, Error> {
         let response = if mechanism.supports_initial_response() || challenge.is_some() {
-            Some(mechanism.response(&credentials, challenge.as_ref().map(String::as_str))?)
+            Some(mechanism.response(&credentials, challenge.as_deref())?)
         } else {
             None
         };
-        Ok(AuthCommand {
+        Ok(Auth {
             mechanism,
             credentials,
             challenge,
@@ -263,7 +259,7 @@ impl AuthCommand {
         mechanism: Mechanism,
         credentials: Credentials,
         response: &Response,
-    ) -> Result<AuthCommand, Error> {
+    ) -> Result<Auth, Error> {
         if !response.has_code(334) {
             return Err(Error::ResponseParsing("Expecting a challenge"));
         }
@@ -271,14 +267,16 @@ impl AuthCommand {
         let encoded_challenge = response
             .first_word()
             .ok_or(Error::ResponseParsing("Could not read auth challenge"))?;
-        debug!("auth encoded challenge: {}", encoded_challenge);
+        #[cfg(feature = "tracing")]
+        tracing::debug!("auth encoded challenge: {}", encoded_challenge);
 
         let decoded_challenge = String::from_utf8(base64::decode(&encoded_challenge)?)?;
-        debug!("auth decoded challenge: {}", decoded_challenge);
+        #[cfg(feature = "tracing")]
+        tracing::debug!("auth decoded challenge: {}", decoded_challenge);
 
         let response = Some(mechanism.response(&credentials, Some(decoded_challenge.as_ref()))?);
 
-        Ok(AuthCommand {
+        Ok(Auth {
             mechanism,
             credentials,
             challenge: Some(decoded_challenge),
@@ -290,12 +288,13 @@ impl AuthCommand {
 #[cfg(test)]
 mod test {
     use super::*;
-    use smtp::extension::MailBodyParameter;
+    use crate::transport::smtp::extension::MailBodyParameter;
+    use std::str::FromStr;
 
     #[test]
     fn test_display() {
         let id = ClientId::Domain("localhost".to_string());
-        let email = EmailAddress::new("test@example.com".to_string()).unwrap();
+        let email = Address::from_str("test@example.com").unwrap();
         let mail_parameter = MailParameter::Other {
             keyword: "TEST".to_string(),
             value: Some("value".to_string()),
@@ -304,26 +303,23 @@ mod test {
             keyword: "TEST".to_string(),
             value: Some("value".to_string()),
         };
-        assert_eq!(format!("{}", EhloCommand::new(id)), "EHLO localhost\r\n");
+        assert_eq!(format!("{}", Ehlo::new(id)), "EHLO localhost\r\n");
         assert_eq!(
-            format!("{}", MailCommand::new(Some(email.clone()), vec![])),
+            format!("{}", Mail::new(Some(email.clone()), vec![])),
             "MAIL FROM:<test@example.com>\r\n"
         );
-        assert_eq!(
-            format!("{}", MailCommand::new(None, vec![])),
-            "MAIL FROM:<>\r\n"
-        );
+        assert_eq!(format!("{}", Mail::new(None, vec![])), "MAIL FROM:<>\r\n");
         assert_eq!(
             format!(
                 "{}",
-                MailCommand::new(Some(email.clone()), vec![MailParameter::Size(42)])
+                Mail::new(Some(email.clone()), vec![MailParameter::Size(42)])
             ),
             "MAIL FROM:<test@example.com> SIZE=42\r\n"
         );
         assert_eq!(
             format!(
                 "{}",
-                MailCommand::new(
+                Mail::new(
                     Some(email.clone()),
                     vec![
                         MailParameter::Size(42),
@@ -335,42 +331,42 @@ mod test {
             "MAIL FROM:<test@example.com> SIZE=42 BODY=8BITMIME TEST=value\r\n"
         );
         assert_eq!(
-            format!("{}", RcptCommand::new(email.clone(), vec![])),
+            format!("{}", Rcpt::new(email.clone(), vec![])),
             "RCPT TO:<test@example.com>\r\n"
         );
         assert_eq!(
-            format!("{}", RcptCommand::new(email.clone(), vec![rcpt_parameter])),
+            format!("{}", Rcpt::new(email, vec![rcpt_parameter])),
             "RCPT TO:<test@example.com> TEST=value\r\n"
         );
-        assert_eq!(format!("{}", QuitCommand), "QUIT\r\n");
-        assert_eq!(format!("{}", DataCommand), "DATA\r\n");
-        assert_eq!(format!("{}", NoopCommand), "NOOP\r\n");
-        assert_eq!(format!("{}", HelpCommand::new(None)), "HELP\r\n");
+        assert_eq!(format!("{}", Quit), "QUIT\r\n");
+        assert_eq!(format!("{}", Data), "DATA\r\n");
+        assert_eq!(format!("{}", Noop), "NOOP\r\n");
+        assert_eq!(format!("{}", Help::new(None)), "HELP\r\n");
         assert_eq!(
-            format!("{}", HelpCommand::new(Some("test".to_string()))),
+            format!("{}", Help::new(Some("test".to_string()))),
             "HELP test\r\n"
         );
         assert_eq!(
-            format!("{}", VrfyCommand::new("test".to_string())),
+            format!("{}", Vrfy::new("test".to_string())),
             "VRFY test\r\n"
         );
         assert_eq!(
-            format!("{}", ExpnCommand::new("test".to_string())),
+            format!("{}", Expn::new("test".to_string())),
             "EXPN test\r\n"
         );
-        assert_eq!(format!("{}", RsetCommand), "RSET\r\n");
+        assert_eq!(format!("{}", Rset), "RSET\r\n");
         let credentials = Credentials::new("user".to_string(), "password".to_string());
         assert_eq!(
             format!(
                 "{}",
-                AuthCommand::new(Mechanism::Plain, credentials.clone(), None).unwrap()
+                Auth::new(Mechanism::Plain, credentials.clone(), None).unwrap()
             ),
             "AUTH PLAIN AHVzZXIAcGFzc3dvcmQ=\r\n"
         );
         assert_eq!(
             format!(
                 "{}",
-                AuthCommand::new(Mechanism::Login, credentials.clone(), None).unwrap()
+                Auth::new(Mechanism::Login, credentials, None).unwrap()
             ),
             "AUTH LOGIN\r\n"
         );

src/transport/smtp/error.rs

@@ -0,0 +1,162 @@
+//! Error and result type for SMTP clients
+
+use self::Error::*;
+use crate::transport::smtp::response::{Response, Severity};
+use base64::DecodeError;
+use std::{
+    error::Error as StdError,
+    fmt::{self, Display, Formatter},
+    io,
+    string::FromUtf8Error,
+};
+
+/// An enum of all error kinds.
+#[derive(Debug)]
+pub enum Error {
+    /// Transient SMTP error, 4xx reply code
+    ///
+    /// [RFC 5321, section 4.2.1](https://tools.ietf.org/html/rfc5321#section-4.2.1)
+    Transient(Response),
+    /// Permanent SMTP error, 5xx reply code
+    ///
+    /// [RFC 5321, section 4.2.1](https://tools.ietf.org/html/rfc5321#section-4.2.1)
+    Permanent(Response),
+    /// Error parsing a response
+    ResponseParsing(&'static str),
+    /// Error parsing a base64 string in response
+    ChallengeParsing(DecodeError),
+    /// Error parsing UTF8 in response
+    Utf8Parsing(FromUtf8Error),
+    /// Internal client error
+    Client(&'static str),
+    /// DNS resolution error
+    Resolution,
+    /// IO error
+    Io(io::Error),
+    /// TLS error
+    #[cfg(feature = "native-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+    Tls(native_tls::Error),
+    /// Parsing error
+    Parsing(nom::error::ErrorKind),
+    /// Invalid hostname
+    #[cfg(feature = "rustls-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "rustls-tls")))]
+    InvalidDNSName(webpki::InvalidDNSNameError),
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "rustls-tls"))))]
+    InvalidCertificate,
+    #[cfg(feature = "r2d2")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "r2d2")))]
+    Pool(r2d2::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), fmt::Error> {
+        match *self {
+            // Try to display the first line of the server's response that usually
+            // contains a short humanly readable error message
+            Transient(ref err) => fmt.write_str(
+                err.first_line()
+                    .unwrap_or("transient error during SMTP transaction"),
+            ),
+            Permanent(ref err) => fmt.write_str(
+                err.first_line()
+                    .unwrap_or("permanent error during SMTP transaction"),
+            ),
+            ResponseParsing(err) => fmt.write_str(err),
+            ChallengeParsing(ref err) => err.fmt(fmt),
+            Utf8Parsing(ref err) => err.fmt(fmt),
+            Resolution => fmt.write_str("could not resolve hostname"),
+            Client(err) => fmt.write_str(err),
+            Io(ref err) => err.fmt(fmt),
+            #[cfg(feature = "native-tls")]
+            Tls(ref err) => err.fmt(fmt),
+            Parsing(ref err) => fmt.write_str(err.description()),
+            #[cfg(feature = "rustls-tls")]
+            InvalidDNSName(ref err) => err.fmt(fmt),
+            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+            InvalidCertificate => fmt.write_str("invalid certificate"),
+            #[cfg(feature = "r2d2")]
+            Pool(ref err) => err.fmt(fmt),
+        }
+    }
+}
+
+impl StdError for Error {
+    fn source(&self) -> Option<&(dyn StdError + 'static)> {
+        match *self {
+            ChallengeParsing(ref err) => Some(&*err),
+            Utf8Parsing(ref err) => Some(&*err),
+            Io(ref err) => Some(&*err),
+            #[cfg(feature = "native-tls")]
+            Tls(ref err) => Some(&*err),
+            _ => None,
+        }
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(err: io::Error) -> Error {
+        Io(err)
+    }
+}
+
+#[cfg(feature = "native-tls")]
+impl From<native_tls::Error> for Error {
+    fn from(err: native_tls::Error) -> Error {
+        Tls(err)
+    }
+}
+
+impl From<nom::Err<nom::error::Error<&str>>> for Error {
+    fn from(err: nom::Err<nom::error::Error<&str>>) -> Error {
+        Parsing(match err {
+            nom::Err::Incomplete(_) => nom::error::ErrorKind::Complete,
+            nom::Err::Failure(e) => e.code,
+            nom::Err::Error(e) => e.code,
+        })
+    }
+}
+
+impl From<DecodeError> for Error {
+    fn from(err: DecodeError) -> Error {
+        ChallengeParsing(err)
+    }
+}
+
+impl From<FromUtf8Error> for Error {
+    fn from(err: FromUtf8Error) -> Error {
+        Utf8Parsing(err)
+    }
+}
+
+#[cfg(feature = "rustls-tls")]
+impl From<webpki::InvalidDNSNameError> for Error {
+    fn from(err: webpki::InvalidDNSNameError) -> Error {
+        InvalidDNSName(err)
+    }
+}
+
+#[cfg(feature = "r2d2")]
+impl From<r2d2::Error> for Error {
+    fn from(err: r2d2::Error) -> Error {
+        Pool(err)
+    }
+}
+
+impl From<Response> for Error {
+    fn from(response: Response) -> Error {
+        match response.code.severity {
+            Severity::TransientNegativeCompletion => Transient(response),
+            Severity::PermanentNegativeCompletion => Permanent(response),
+            _ => Client("Unknown error code"),
+        }
+    }
+}
+
+impl From<&'static str> for Error {
+    fn from(string: &'static str) -> Error {
+        Client(string)
+    }
+}

src/transport/smtp/extension.rs

@@ -1,21 +1,19 @@
 //! ESMTP features
 
-use hostname::get_hostname;
-use smtp::authentication::Mechanism;
-use smtp::error::Error;
-use smtp::response::Response;
-use smtp::util::XText;
-use std::collections::HashSet;
-use std::fmt::{self, Display, Formatter};
-use std::net::{Ipv4Addr, Ipv6Addr};
-use std::result::Result;
-
-/// Default client id
-pub const DEFAULT_DOMAIN_CLIENT_ID: &str = "localhost";
+use crate::transport::smtp::{
+    authentication::Mechanism, error::Error, response::Response, util::XText,
+};
+use std::{
+    collections::HashSet,
+    fmt::{self, Display, Formatter},
+    net::{Ipv4Addr, Ipv6Addr},
+    result::Result,
+};
 
 /// Client identifier, the parameter to `EHLO`
 #[derive(PartialEq, Eq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[non_exhaustive]
 pub enum ClientId {
     /// A fully-qualified domain name
     Domain(String),
@@ -25,63 +23,82 @@ pub enum ClientId {
     Ipv6(Ipv6Addr),
 }
 
+const LOCALHOST_CLIENT: ClientId = ClientId::Ipv4(Ipv4Addr::new(127, 0, 0, 1));
+
+impl Default for ClientId {
+    fn default() -> Self {
+        // https://tools.ietf.org/html/rfc5321#section-4.1.4
+        //
+        // The SMTP client MUST, if possible, ensure that the domain parameter
+        // to the EHLO command is a primary host name as specified for this
+        // command in Section 2.3.5.  If this is not possible (e.g., when the
+        // client's address is dynamically assigned and the client does not have
+        // an obvious name), an address literal SHOULD be substituted for the
+        // domain name.
+        #[cfg(feature = "hostname")]
+        {
+            hostname::get()
+                .ok()
+                .and_then(|s| s.into_string().map(Self::Domain).ok())
+                .unwrap_or(LOCALHOST_CLIENT)
+        }
+        #[cfg(not(feature = "hostname"))]
+        LOCALHOST_CLIENT
+    }
+}
+
 impl Display for ClientId {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match *self {
-            ClientId::Domain(ref value) => f.write_str(value),
-            ClientId::Ipv4(ref value) => write!(f, "{}", value),
-            ClientId::Ipv6(ref value) => write!(f, "{}", value),
+            Self::Domain(ref value) => f.write_str(value),
+            Self::Ipv4(ref value) => write!(f, "[{}]", value),
+            Self::Ipv6(ref value) => write!(f, "[IPv6:{}]", value),
         }
     }
 }
 
 impl ClientId {
+    #[deprecated(since = "0.10.0", note = "Please use ClientId::Domain(domain) instead")]
     /// Creates a new `ClientId` from a fully qualified domain name
-    pub fn new(domain: String) -> ClientId {
-        ClientId::Domain(domain)
-    }
-
-    /// Defines a `ClientId` with the current hostname, of `localhost` if hostname could not be
-    /// found
-    pub fn hostname() -> ClientId {
-        ClientId::Domain(get_hostname().unwrap_or_else(|| DEFAULT_DOMAIN_CLIENT_ID.to_string()))
+    pub fn new(domain: String) -> Self {
+        Self::Domain(domain)
     }
 }
 
 /// Supported ESMTP keywords
 #[derive(PartialEq, Eq, Hash, Copy, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum Extension {
     /// 8BITMIME keyword
     ///
-    /// RFC 6152: https://tools.ietf.org/html/rfc6152
+    /// Defined in [RFC 6152](https://tools.ietf.org/html/rfc6152)
     EightBitMime,
     /// SMTPUTF8 keyword
     ///
-    /// RFC 6531: https://tools.ietf.org/html/rfc6531
+    /// Defined in [RFC 6531](https://tools.ietf.org/html/rfc6531)
     SmtpUtfEight,
     /// STARTTLS keyword
     ///
-    /// RFC 2487: https://tools.ietf.org/html/rfc2487
+    /// Defined in [RFC 2487](https://tools.ietf.org/html/rfc2487)
     StartTls,
     /// AUTH mechanism
     Authentication(Mechanism),
 }
 
 impl Display for Extension {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match *self {
-            Extension::EightBitMime => write!(f, "8BITMIME"),
-            Extension::SmtpUtfEight => write!(f, "SMTPUTF8"),
-            Extension::StartTls => write!(f, "STARTTLS"),
+            Extension::EightBitMime => f.write_str("8BITMIME"),
+            Extension::SmtpUtfEight => f.write_str("SMTPUTF8"),
+            Extension::StartTls => f.write_str("STARTTLS"),
             Extension::Authentication(ref mechanism) => write!(f, "AUTH {}", mechanism),
         }
     }
 }
 
 /// Contains information about an SMTP server
-#[derive(Clone, Debug, Eq, PartialEq)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[derive(Clone, Debug, Eq, PartialEq, Default)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct ServerInfo {
     /// Server name
     ///
@@ -94,17 +111,13 @@ pub struct ServerInfo {
 }
 
 impl Display for ServerInfo {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(
-            f,
-            "{} with {}",
-            self.name,
-            if self.features.is_empty() {
-                "no supported features".to_string()
-            } else {
-                format!("{:?}", self.features)
-            }
-        )
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let features = if self.features.is_empty() {
+            "no supported features".to_string()
+        } else {
+            format!("{:?}", self.features)
+        };
+        write!(f, "{} with {}", self.name, features)
     }
 }
 
@@ -123,8 +136,8 @@ impl ServerInfo {
                 continue;
             }
 
-            let split: Vec<&str> = line.split_whitespace().collect();
-            match split[0] {
+            let mut split = line.split_whitespace();
+            match split.next().unwrap() {
                 "8BITMIME" => {
                     features.insert(Extension::EightBitMime);
                 }
@@ -135,7 +148,7 @@ impl ServerInfo {
                     features.insert(Extension::StartTls);
                 }
                 "AUTH" => {
-                    for &mechanism in &split[1..] {
+                    for mechanism in split {
                         match mechanism {
                             "PLAIN" => {
                                 features.insert(Extension::Authentication(Mechanism::Plain));
@@ -170,11 +183,21 @@ impl ServerInfo {
         self.features
             .contains(&Extension::Authentication(mechanism))
     }
+
+    /// Gets a compatible mechanism from list
+    pub fn get_auth_mechanism(&self, mechanisms: &[Mechanism]) -> Option<Mechanism> {
+        for mechanism in mechanisms {
+            if self.supports_auth_mechanism(*mechanism) {
+                return Some(*mechanism);
+            }
+        }
+        None
+    }
 }
 
 /// A `MAIL FROM` extension parameter
 #[derive(PartialEq, Eq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum MailParameter {
     /// `BODY` parameter
     Body(MailBodyParameter),
@@ -192,7 +215,7 @@ pub enum MailParameter {
 }
 
 impl Display for MailParameter {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match *self {
             MailParameter::Body(ref value) => write!(f, "BODY={}", value),
             MailParameter::Size(size) => write!(f, "SIZE={}", size),
@@ -211,7 +234,7 @@ impl Display for MailParameter {
 
 /// Values for the `BODY` parameter to `MAIL FROM`
 #[derive(PartialEq, Eq, Clone, Debug, Copy)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum MailBodyParameter {
     /// `7BIT`
     SevenBit,
@@ -220,7 +243,7 @@ pub enum MailBodyParameter {
 }
 
 impl Display for MailBodyParameter {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match *self {
             MailBodyParameter::SevenBit => f.write_str("7BIT"),
             MailBodyParameter::EightBitMime => f.write_str("8BITMIME"),
@@ -230,7 +253,7 @@ impl Display for MailBodyParameter {
 
 /// A `RCPT TO` extension parameter
 #[derive(PartialEq, Eq, Clone, Debug)]
-#[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum RcptParameter {
     /// Custom parameter
     Other {
@@ -242,7 +265,7 @@ pub enum RcptParameter {
 }
 
 impl Display for RcptParameter {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match *self {
             RcptParameter::Other {
                 ref keyword,
@@ -259,17 +282,20 @@ impl Display for RcptParameter {
 #[cfg(test)]
 mod test {
 
-    use super::{ClientId, Extension, ServerInfo};
-    use smtp::authentication::Mechanism;
-    use smtp::response::{Category, Code, Detail, Response, Severity};
+    use super::*;
+    use crate::transport::smtp::{
+        authentication::Mechanism,
+        response::{Category, Code, Detail, Response, Severity},
+    };
     use std::collections::HashSet;
 
     #[test]
     fn test_clientid_fmt() {
         assert_eq!(
-            format!("{}", ClientId::new("test".to_string())),
+            format!("{}", ClientId::Domain("test".to_string())),
             "test".to_string()
         );
+        assert_eq!(format!("{}", LOCALHOST_CLIENT), "[127.0.0.1]".to_string());
     }
 
     #[test]
@@ -294,7 +320,7 @@ mod test {
                 "{}",
                 ServerInfo {
                     name: "name".to_string(),
-                    features: eightbitmime.clone(),
+                    features: eightbitmime,
                 }
             ),
             "name with {EightBitMime}".to_string()
@@ -321,7 +347,7 @@ mod test {
                 "{}",
                 ServerInfo {
                     name: "name".to_string(),
-                    features: plain.clone(),
+                    features: plain,
                 }
             ),
             "name with {Authentication(Plain)}".to_string()