Prepare 0.10.0-beta.1 (#555)

* Executor
* Move transports inside the transport module
* AsyncTransport refactor
* Update examples
* Update docs
* impl Default for AsyncSendmailTransport
* Implement AsyncFileTransport::read
* Generalize AsyncFileTransport AsyncTransport implementation
* Remove remaining uses of AsyncSmtpConnector

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "lettre"
 # remember to update html_root_url and README.md (Cargo.toml example and deps.rs badge)
-version = "0.10.0-alpha.5"
+version = "0.10.0-beta.1"
 description = "Email client"
 readme = "README.md"
 homepage = "https://lettre.rs"
@@ -23,7 +23,7 @@ tracing = { version = "0.1.16", default-features = false, features = ["std"], op
 
 # builder
 hyperx = { version = "1", optional = true, features = ["headers"] }
-mime = { version = "0.3", optional = true }
+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 }
@@ -80,7 +80,7 @@ harness = false
 name = "transport_smtp"
 
 [features]
-default = ["file-transport", "file-transport-envelope", "smtp-transport", "native-tls", "hostname", "r2d2", "sendmail-transport", "builder"]
+default = ["smtp-transport", "native-tls", "hostname", "r2d2", "builder"]
 builder = ["mime", "base64", "hyperx", "rand", "quoted_printable"]
 
 # transports

README.md

@@ -28,8 +28,8 @@
 </div>
 
 <div align="center">
-  <a href="https://deps.rs/crate/lettre/0.10.0-alpha.4">
-    <img src="https://deps.rs/crate/lettre/0.10.0-alpha.4/status.svg"
+  <a href="https://deps.rs/crate/lettre/0.10.0-beta.1">
+    <img src="https://deps.rs/crate/lettre/0.10.0-beta.1/status.svg"
       alt="dependency status" />
   </a>
 </div>
@@ -66,7 +66,7 @@ To use this library, add the following to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-lettre = "0.10.0-alpha.4"
+lettre = "0.10.0-beta.1"
 ```
 
 ```rust,no_run

examples/asyncstd1_smtp_starttls.rs

@@ -1,5 +1,5 @@
 use lettre::{
-    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncStd1Connector,
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncStd1Executor,
     AsyncStd1Transport, Message,
 };
 
@@ -18,10 +18,11 @@ async fn main() {
     let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
     // Open a remote connection to gmail using STARTTLS
-    let mailer = AsyncSmtpTransport::<AsyncStd1Connector>::starttls_relay("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .build();
+    let mailer: AsyncSmtpTransport<AsyncStd1Executor> =
+        AsyncSmtpTransport::<AsyncStd1Executor>::starttls_relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
 
     // Send the email
     match mailer.send(email).await {

examples/asyncstd1_smtp_tls.rs

@@ -1,5 +1,5 @@
 use lettre::{
-    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncStd1Connector,
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncStd1Executor,
     AsyncStd1Transport, Message,
 };
 
@@ -18,10 +18,11 @@ async fn main() {
     let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
     // Open a remote connection to gmail
-    let mailer = AsyncSmtpTransport::<AsyncStd1Connector>::relay("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .build();
+    let mailer: AsyncSmtpTransport<AsyncStd1Executor> =
+        AsyncSmtpTransport::<AsyncStd1Executor>::relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
 
     // Send the email
     match mailer.send(email).await {

examples/basic_html.rs

@@ -1,5 +1,7 @@
-use lettre::message::{header, MultiPart, SinglePart};
-use lettre::{FileTransport, Message, Transport};
+use lettre::{
+    message::{header, MultiPart, SinglePart},
+    FileTransport, Message, Transport,
+};
 
 fn main() {
     // The html we want to send.

examples/maud_html.rs

@@ -1,5 +1,7 @@
-use lettre::message::{header, MultiPart, SinglePart};
-use lettre::{FileTransport, Message, Transport};
+use lettre::{
+    message::{header, MultiPart, SinglePart},
+    FileTransport, Message, Transport,
+};
 use maud::html;
 
 fn main() {

examples/smtp_selfsigned.rs

@@ -1,8 +1,10 @@
 use std::fs;
 
 use lettre::{
-    transport::smtp::authentication::Credentials,
-    transport::smtp::client::{Certificate, Tls, TlsParameters},
+    transport::smtp::{
+        authentication::Credentials,
+        client::{Certificate, Tls, TlsParameters},
+    },
     Message, SmtpTransport, Transport,
 };
 
@@ -20,9 +22,10 @@ fn main() {
     // 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 mut tls = TlsParameters::builder("smtp.server.com".to_string());
-    tls.add_root_certificate(cert);
-    let tls = tls.build().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());
 

examples/tokio02_smtp_starttls.rs

@@ -4,7 +4,7 @@
 use tokio02_crate as tokio;
 
 use lettre::{
-    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio02Connector,
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio02Executor,
     Tokio02Transport,
 };
 
@@ -23,10 +23,11 @@ async fn main() {
     let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
     // Open a remote connection to gmail using STARTTLS
-    let mailer = AsyncSmtpTransport::<Tokio02Connector>::starttls_relay("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .build();
+    let mailer: AsyncSmtpTransport<Tokio02Executor> =
+        AsyncSmtpTransport::<Tokio02Executor>::starttls_relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
 
     // Send the email
     match mailer.send(email).await {

examples/tokio02_smtp_tls.rs

@@ -4,7 +4,7 @@
 use tokio02_crate as tokio;
 
 use lettre::{
-    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio02Connector,
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio02Executor,
     Tokio02Transport,
 };
 
@@ -23,10 +23,11 @@ async fn main() {
     let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
     // Open a remote connection to gmail
-    let mailer = AsyncSmtpTransport::<Tokio02Connector>::relay("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .build();
+    let mailer: AsyncSmtpTransport<Tokio02Executor> =
+        AsyncSmtpTransport::<Tokio02Executor>::relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
 
     // Send the email
     match mailer.send(email).await {

examples/tokio1_smtp_starttls.rs

@@ -4,7 +4,7 @@
 use tokio1_crate as tokio;
 
 use lettre::{
-    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio1Connector,
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio1Executor,
     Tokio1Transport,
 };
 
@@ -23,10 +23,11 @@ async fn main() {
     let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
     // Open a remote connection to gmail using STARTTLS
-    let mailer = AsyncSmtpTransport::<Tokio1Connector>::starttls_relay("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .build();
+    let mailer: AsyncSmtpTransport<Tokio1Executor> =
+        AsyncSmtpTransport::<Tokio1Executor>::starttls_relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
 
     // Send the email
     match mailer.send(email).await {

examples/tokio1_smtp_tls.rs

@@ -4,7 +4,7 @@
 use tokio1_crate as tokio;
 
 use lettre::{
-    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio1Connector,
+    transport::smtp::authentication::Credentials, AsyncSmtpTransport, Message, Tokio1Executor,
     Tokio1Transport,
 };
 
@@ -23,10 +23,11 @@ async fn main() {
     let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
 
     // Open a remote connection to gmail
-    let mailer = AsyncSmtpTransport::<Tokio1Connector>::relay("smtp.gmail.com")
-        .unwrap()
-        .credentials(creds)
-        .build();
+    let mailer: AsyncSmtpTransport<Tokio1Executor> =
+        AsyncSmtpTransport::<Tokio1Executor>::relay("smtp.gmail.com")
+            .unwrap()
+            .credentials(creds)
+            .build();
 
     // Send the email
     match mailer.send(email).await {

src/address/envelope.rs

@@ -103,6 +103,14 @@ impl Envelope {
     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")]

src/address/mod.rs

@@ -1,8 +1,12 @@
+//! Email addresses
+
 #[cfg(feature = "serde")]
 mod serde;
 
 mod envelope;
 mod types;
 
-pub use self::envelope::Envelope;
-pub use self::types::{Address, AddressError};
+pub use self::{
+    envelope::Envelope,
+    types::{Address, AddressError},
+};

src/address/types.rs

@@ -173,6 +173,11 @@ impl Address {
 
         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 {
@@ -211,6 +216,7 @@ impl AsRef<OsStr> for Address {
 }
 
 #[derive(Debug, PartialEq, Clone, Copy)]
+/// Errors in email addresses parsing
 pub enum AddressError {
     MissingParts,
     Unbalanced,

src/error.rs

@@ -1,3 +1,5 @@
+//! Error type for email messages
+
 use std::{
     error::Error as StdError,
     fmt::{self, Display, Formatter},

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

@@ -30,7 +30,7 @@
 //! * **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-alpha.5")]
+#![doc(html_root_url = "https://docs.rs/crate/lettre/0.10.0-beta.1")]
 #![doc(html_favicon_url = "https://lettre.rs/favicon.ico")]
 #![doc(html_logo_url = "https://avatars0.githubusercontent.com/u/15113230?v=4")]
 #![forbid(unsafe_code)]
@@ -46,6 +46,8 @@
 
 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;
@@ -55,13 +57,31 @@ pub mod transport;
 #[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;
-use crate::address::Envelope;
-use crate::error::Error;
 #[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(
@@ -69,103 +89,32 @@ pub use crate::transport::sendmail::SendmailTransport;
     any(feature = "tokio02", feature = "tokio1")
 ))]
 pub use crate::transport::smtp::AsyncSmtpTransport;
+pub use crate::transport::Transport;
+use crate::{address::Envelope, error::Error};
+
+#[doc(hidden)]
+#[allow(deprecated)]
 #[cfg(all(feature = "smtp-transport", feature = "async-std1"))]
 pub use crate::transport::smtp::AsyncStd1Connector;
 #[cfg(feature = "smtp-transport")]
 pub use crate::transport::smtp::SmtpTransport;
+#[doc(hidden)]
+#[allow(deprecated)]
 #[cfg(all(feature = "smtp-transport", feature = "tokio02"))]
 pub use crate::transport::smtp::Tokio02Connector;
+#[doc(hidden)]
+#[allow(deprecated)]
 #[cfg(all(feature = "smtp-transport", feature = "tokio1"))]
 pub use crate::transport::smtp::Tokio1Connector;
-#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
-use async_trait::async_trait;
-
-/// 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-std 1.x based Transport method for emails
+#[doc(hidden)]
 #[cfg(feature = "async-std1")]
-#[cfg_attr(docsrs, doc(cfg(feature = "async-std1")))]
-#[async_trait]
-pub trait AsyncStd1Transport {
-    /// 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>;
-}
-
-/// tokio 0.2.x based Transport method for emails
+pub use crate::transport::AsyncStd1Transport;
+#[doc(hidden)]
 #[cfg(feature = "tokio02")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tokio02")))]
-#[async_trait]
-pub trait Tokio02Transport {
-    /// 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>;
-}
-
-/// tokio 1.x based Transport method for emails
+pub use crate::transport::Tokio02Transport;
+#[doc(hidden)]
 #[cfg(feature = "tokio1")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
-#[async_trait]
-pub trait Tokio1Transport {
-    /// 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>;
-}
+pub use crate::transport::Tokio1Transport;
 
 #[cfg(test)]
 #[cfg(feature = "builder")]

src/message/body.rs

@@ -1,5 +1,7 @@
-use std::io::{self, Write};
-use std::ops::Deref;
+use std::{
+    io::{self, Write},
+    ops::Deref,
+};
 
 use crate::message::header::ContentTransferEncoding;
 

src/message/header/content.rs

@@ -7,7 +7,10 @@ use std::{
     str::{from_utf8, FromStr},
 };
 
-header! { (ContentId, "Content-ID") => [String] }
+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
 ///

src/message/header/mod.rs

@@ -1,8 +1,4 @@
-/*!
-
-## Headers widely used in email messages
-
-*/
+//! Headers widely used in email messages
 
 mod content;
 mod mailbox;

src/message/header/special.rs

@@ -5,6 +5,7 @@ use hyperx::{
 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,

src/message/header/textual.rs

@@ -6,8 +6,9 @@ use hyperx::{
 use std::{fmt::Result as FmtResult, str::from_utf8};
 
 macro_rules! text_header {
-    ( $type_name: ident, $header_name: expr ) => {
+    ($(#[$attr:meta])* Header($type_name: ident, $header_name: expr )) => {
         #[derive(Debug, Clone, PartialEq)]
+        $(#[$attr])*
         pub struct $type_name(pub String);
 
         impl Header for $type_name {
@@ -33,13 +34,41 @@ macro_rules! text_header {
     };
 }
 
-text_header!(Subject, "Subject");
-text_header!(Comments, "Comments");
-text_header!(Keywords, "Keywords");
-text_header!(InReplyTo, "In-Reply-To");
-text_header!(References, "References");
-text_header!(MessageId, "Message-Id");
-text_header!(UserAgent, "User-Agent");
+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) {

src/message/mailbox/types.rs

@@ -54,7 +54,7 @@ impl Mailbox {
     /// # Examples
     ///
     /// ```
-    /// use lettre::{Address, message::Mailbox};
+    /// use lettre::{message::Mailbox, Address};
     ///
     /// # use std::error::Error;
     /// # fn main() -> Result<(), Box<dyn Error>> {
@@ -163,7 +163,10 @@ impl Mailboxes {
     /// # Examples
     ///
     /// ```
-    /// use lettre::{Address, message::{Mailbox, Mailboxes}};
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
     ///
     /// # use std::error::Error;
     /// # fn main() -> Result<(), Box<dyn Error>> {
@@ -182,7 +185,10 @@ impl Mailboxes {
     /// # Examples
     ///
     /// ```
-    /// use lettre::{Address, message::{Mailbox, Mailboxes}};
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
     ///
     /// # use std::error::Error;
     /// # fn main() -> Result<(), Box<dyn Error>> {
@@ -201,7 +207,10 @@ impl Mailboxes {
     /// # Examples
     ///
     /// ```
-    /// use lettre::{Address, message::{Mailbox, Mailboxes}};
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
     ///
     /// # use std::error::Error;
     /// # fn main() -> Result<(), Box<dyn Error>> {
@@ -225,7 +234,10 @@ impl Mailboxes {
     /// # Examples
     ///
     /// ```
-    /// use lettre::{Address, message::{Mailbox, Mailboxes}};
+    /// use lettre::{
+    ///     message::{Mailbox, Mailboxes},
+    ///     Address,
+    /// };
     ///
     /// # use std::error::Error;
     /// # fn main() -> Result<(), Box<dyn Error>> {

src/message/mimebody.rs

@@ -6,15 +6,12 @@ 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),
 }
 
@@ -37,11 +34,9 @@ impl Part {
 }
 
 /// Parts of multipart body
-///
 pub type Parts = Vec<Part>;
 
 /// Creates builder for single part
-///
 #[derive(Debug, Clone)]
 pub struct SinglePartBuilder {
     headers: Headers,
@@ -92,17 +87,16 @@ impl Default for SinglePartBuilder {
 /// # Example
 ///
 /// ```
-/// use lettre::message::{SinglePart, header};
+/// 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"));
+///     .header(header::ContentType("text/plain; charset=utf8".parse()?))
+///     .body(String::from("Текст письма в уникоде"));
 /// # Ok(())
 /// # }
 /// ```
-///
 #[derive(Debug, Clone)]
 pub struct SinglePart {
     headers: Headers,
@@ -116,30 +110,6 @@ impl SinglePart {
         SinglePartBuilder::new()
     }
 
-    #[doc(hidden)]
-    #[deprecated = "Replaced by SinglePart::builder(), which chooses the best Content-Transfer-Encoding based on the provided body"]
-    pub fn seven_bit() -> SinglePartBuilder {
-        Self::builder().header(ContentTransferEncoding::SevenBit)
-    }
-
-    #[doc(hidden)]
-    #[deprecated = "Replaced by SinglePart::builder(), which chooses the best Content-Transfer-Encoding based on the provided body"]
-    pub fn quoted_printable() -> SinglePartBuilder {
-        Self::builder().header(ContentTransferEncoding::QuotedPrintable)
-    }
-
-    #[doc(hidden)]
-    #[deprecated = "Replaced by SinglePart::builder(), which chooses the best Content-Transfer-Encoding based on the provided body"]
-    pub fn base64() -> SinglePartBuilder {
-        Self::builder().header(ContentTransferEncoding::Base64)
-    }
-
-    #[doc(hidden)]
-    #[deprecated = "Replaced by SinglePart::builder(), which chooses the best Content-Transfer-Encoding based on the provided body"]
-    pub fn eight_bit() -> SinglePartBuilder {
-        Self::builder().header(ContentTransferEncoding::EightBit)
-    }
-
     /// Get the headers from singlepart
     #[inline]
     pub fn headers(&self) -> &Headers {
@@ -170,7 +140,6 @@ impl EmailFormat for SinglePart {
 }
 
 /// The kind of multipart
-///
 #[derive(Debug, Clone)]
 pub enum MultiPartKind {
     /// Mixed kind to combine unrelated content parts
@@ -257,7 +226,6 @@ impl From<MultiPartKind> for Mime {
 }
 
 /// Multipart builder
-///
 #[derive(Debug, Clone)]
 pub struct MultiPartBuilder {
     headers: Headers,
@@ -323,7 +291,6 @@ impl Default for MultiPartBuilder {
 }
 
 /// Multipart variant with parts
-///
 #[derive(Debug, Clone)]
 pub struct MultiPart {
     headers: Headers,

src/message/mod.rs

@@ -114,7 +114,6 @@
 //!
 //! <p><b>Hello</b>, <i>world</i>! <img src="cid:123"></p>
 //! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1--
-//!
 //! ```
 //! </details>
 //!
@@ -125,8 +124,8 @@
 //!
 //! ```rust
 //! # use std::error::Error;
+//! use lettre::message::{header, Body, Message, MultiPart, Part, SinglePart};
 //! use std::fs;
-//! use lettre::message::{Body, header, Message, MultiPart, Part, SinglePart};
 //!
 //! # fn main() -> Result<(), Box<dyn Error>> {
 //! let image = fs::read("docs/lettre.png")?;
@@ -236,7 +235,6 @@
 //!
 //! fn main() { println!("Hello, World!") }
 //! --0oVZ2r6AoLAhLlb0gPNSKy6BEqdS2IfwxrcbUuo1--
-//!
 //! ```
 //! </details>
 
@@ -252,8 +250,7 @@ mod mailbox;
 mod mimebody;
 mod utf8_b;
 
-use std::convert::TryFrom;
-use std::time::SystemTime;
+use std::{convert::TryFrom, time::SystemTime};
 
 use uuid::Uuid;
 
@@ -265,7 +262,8 @@ use crate::{
 
 const DEFAULT_MESSAGE_ID_DOMAIN: &str = "localhost";
 
-pub trait EmailFormat {
+/// Something that can be formatted as an email message
+trait EmailFormat {
     // Use a writer?
     fn format(&self, out: &mut Vec<u8>);
 }
@@ -334,7 +332,7 @@ impl MessageBuilder {
 
     /// Set `Sender` header. Should be used when providing several `From` mailboxes.
     ///
-    /// https://tools.ietf.org/html/rfc5322#section-3.6.2
+    /// 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 {
@@ -343,7 +341,7 @@ impl MessageBuilder {
 
     /// Set or add mailbox to `From` header
     ///
-    /// https://tools.ietf.org/html/rfc5322#section-3.6.2
+    /// 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 {
@@ -352,7 +350,7 @@ impl MessageBuilder {
 
     /// Set or add mailbox to `ReplyTo` header
     ///
-    /// https://tools.ietf.org/html/rfc5322#section-3.6.2
+    /// 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 {

src/transport/file/mod.rs

@@ -9,8 +9,8 @@
 //!
 //! # #[cfg(all(feature = "file-transport", feature = "builder"))]
 //! # fn main() -> Result<(), Box<dyn Error>> {
+//! use lettre::{FileTransport, Message, Transport};
 //! use std::env::temp_dir;
-//! use lettre::{Transport, Message, FileTransport};
 //!
 //! // Write to the local temp directory
 //! let sender = FileTransport::new(temp_dir());
@@ -41,8 +41,8 @@
 //!
 //! # #[cfg(all(feature = "file-transport-envelope", feature = "builder"))]
 //! # fn main() -> Result<(), Box<dyn Error>> {
+//! use lettre::{FileTransport, Message, Transport};
 //! use std::env::temp_dir;
-//! use lettre::{Transport, Message, FileTransport};
 //!
 //! // Write to the local temp directory
 //! let sender = FileTransport::with_envelope(temp_dir());
@@ -70,10 +70,10 @@
 //! # #[cfg(all(feature = "tokio1", feature = "file-transport", feature = "builder"))]
 //! # async fn run() -> Result<(), Box<dyn Error>> {
 //! use std::env::temp_dir;
-//! use lettre::{Tokio1Transport, Message, FileTransport};
+//! use lettre::{AsyncTransport, Tokio1Executor, Message, AsyncFileTransport};
 //!
 //! // Write to the local temp directory
-//! let sender = FileTransport::new(temp_dir());
+//! let sender = AsyncFileTransport::<Tokio1Executor>::new(temp_dir());
 //! let email = Message::builder()
 //!     .from("NoBody <nobody@domain.tld>".parse()?)
 //!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
@@ -95,10 +95,10 @@
 //! # #[cfg(all(feature = "async-std1", feature = "file-transport", feature = "builder"))]
 //! # async fn run() -> Result<(), Box<dyn Error>> {
 //! use std::env::temp_dir;
-//! use lettre::{AsyncStd1Transport, Message, FileTransport};
+//! use lettre::{AsyncTransport, AsyncStd1Executor, Message, AsyncFileTransport};
 //!
 //! // Write to the local temp directory
-//! let sender = FileTransport::new(temp_dir());
+//! let sender = AsyncFileTransport::<AsyncStd1Executor>::new(temp_dir());
 //! let email = Message::builder()
 //!     .from("NoBody <nobody@domain.tld>".parse()?)
 //!     .reply_to("Yuin <yuin@domain.tld>".parse()?)
@@ -133,16 +133,13 @@
 //! ```
 
 pub use self::error::Error;
-use crate::address::Envelope;
-#[cfg(feature = "async-std1")]
-use crate::AsyncStd1Transport;
-#[cfg(feature = "tokio02")]
-use crate::Tokio02Transport;
-#[cfg(feature = "tokio1")]
-use crate::Tokio1Transport;
-use crate::Transport;
+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,
@@ -162,6 +159,14 @@ pub struct FileTransport {
     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
     ///
@@ -187,11 +192,71 @@ impl FileTransport {
         }
     }
 
+    /// 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;
@@ -218,80 +283,27 @@ impl Transport for FileTransport {
     }
 }
 
-#[cfg(feature = "async-std1")]
+#[cfg(any(feature = "async-std1", feature = "tokio02", feature = "tokio1"))]
 #[async_trait]
-impl AsyncStd1Transport for FileTransport {
+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> {
-        use async_std::fs;
-
         let email_id = Uuid::new_v4();
 
-        let file = self.path(&email_id, "eml");
-        fs::write(file, email).await?;
+        let file = self.inner.path(&email_id, "eml");
+        E::fs_write(&file, email).await?;
 
         #[cfg(feature = "file-transport-envelope")]
         {
-            if self.save_envelope {
-                let file = self.path(&email_id, "json");
-                fs::write(file, serde_json::to_string(&envelope)?).await?;
-            }
-        }
-        // use envelope anyway
-        let _ = envelope;
-
-        Ok(email_id.to_string())
-    }
-}
-
-#[cfg(feature = "tokio02")]
-#[async_trait]
-impl Tokio02Transport for FileTransport {
-    type Ok = Id;
-    type Error = Error;
-
-    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
-        use tokio02_crate::fs;
-
-        let email_id = Uuid::new_v4();
-        let file = self.path(&email_id, "eml");
-        fs::write(file, email).await?;
-
-        #[cfg(feature = "file-transport-envelope")]
-        {
-            if self.save_envelope {
-                let file = self.path(&email_id, "json");
-                fs::write(file, serde_json::to_string(&envelope)?).await?;
-            }
-        }
-        // use envelope anyway
-        let _ = envelope;
-
-        Ok(email_id.to_string())
-    }
-}
-
-#[cfg(feature = "tokio1")]
-#[async_trait]
-impl Tokio1Transport for FileTransport {
-    type Ok = Id;
-    type Error = Error;
-
-    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
-        use tokio1_crate::fs;
-
-        let email_id = Uuid::new_v4();
-
-        let file = self.path(&email_id, "eml");
-        fs::write(file, email).await?;
-
-        #[cfg(feature = "file-transport-envelope")]
-        {
-            if self.save_envelope {
-                let file = self.path(&email_id, "json");
-                fs::write(file, serde_json::to_string(&envelope)?).await?;
+            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

src/transport/mod.rs

@@ -16,6 +16,26 @@
 //! * 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;
@@ -26,3 +46,47 @@ pub mod sendmail;
 #[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/mod.rs

@@ -33,7 +33,7 @@
 //!
 //! # #[cfg(all(feature = "tokio02", feature = "sendmail-transport", feature = "builder"))]
 //! # async fn run() -> Result<(), Box<dyn Error>> {
-//! use lettre::{Message, Tokio02Transport, SendmailTransport};
+//! use lettre::{Message, AsyncTransport, Tokio02Executor, AsyncSendmailTransport, SendmailTransport};
 //!
 //! let email = Message::builder()
 //!     .from("NoBody <nobody@domain.tld>".parse()?)
@@ -42,7 +42,7 @@
 //!     .subject("Happy new year")
 //!     .body(String::from("Be happy!"))?;
 //!
-//! let sender = SendmailTransport::new();
+//! let sender = AsyncSendmailTransport::<Tokio02Executor>::new();
 //! let result = sender.send(email).await;
 //! assert!(result.is_ok());
 //! # Ok(())
@@ -56,7 +56,7 @@
 //!
 //! # #[cfg(all(feature = "tokio1", feature = "sendmail-transport", feature = "builder"))]
 //! # async fn run() -> Result<(), Box<dyn Error>> {
-//! use lettre::{Message, Tokio1Transport, SendmailTransport};
+//! use lettre::{Message, AsyncTransport, Tokio1Executor, AsyncSendmailTransport, SendmailTransport};
 //!
 //! let email = Message::builder()
 //!     .from("NoBody <nobody@domain.tld>".parse()?)
@@ -65,7 +65,7 @@
 //!     .subject("Happy new year")
 //!     .body(String::from("Be happy!"))?;
 //!
-//! let sender = SendmailTransport::new();
+//! let sender = AsyncSendmailTransport::<Tokio1Executor>::new();
 //! let result = sender.send(email).await;
 //! assert!(result.is_ok());
 //! # Ok(())
@@ -79,7 +79,7 @@
 //!
 //! # #[cfg(all(feature = "async-std1", feature = "sendmail-transport", feature = "builder"))]
 //! # async fn run() -> Result<(), Box<dyn Error>> {
-//! use lettre::{Message, AsyncStd1Transport, SendmailTransport};
+//! use lettre::{Message, AsyncTransport, AsyncStd1Executor, AsyncSendmailTransport};
 //!
 //! let email = Message::builder()
 //!     .from("NoBody <nobody@domain.tld>".parse()?)
@@ -88,7 +88,7 @@
 //!     .subject("Happy new year")
 //!     .body(String::from("Be happy!"))?;
 //!
-//! let sender = SendmailTransport::new();
+//! let sender = AsyncSendmailTransport::<AsyncStd1Executor>::new();
 //! let result = sender.send(email).await;
 //! assert!(result.is_ok());
 //! # Ok(())
@@ -96,16 +96,19 @@
 //! ```
 
 pub use self::error::Error;
-use crate::address::Envelope;
 #[cfg(feature = "async-std1")]
-use crate::AsyncStd1Transport;
+use crate::AsyncStd1Executor;
 #[cfg(feature = "tokio02")]
-use crate::Tokio02Transport;
+use crate::Tokio02Executor;
 #[cfg(feature = "tokio1")]
-use crate::Tokio1Transport;
-use crate::Transport;
+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::*,
@@ -123,6 +126,14 @@ 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 {
@@ -151,12 +162,34 @@ impl SendmailTransport {
             .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.command);
+        let mut c = Command::new(&self.inner.command);
         c.kill_on_drop(true);
         c.arg("-i");
         if let Some(from) = envelope.from() {
@@ -174,7 +207,7 @@ impl SendmailTransport {
     fn tokio1_command(&self, envelope: &Envelope) -> tokio1_crate::process::Command {
         use tokio1_crate::process::Command;
 
-        let mut c = Command::new(&self.command);
+        let mut c = Command::new(&self.inner.command);
         c.kill_on_drop(true);
         c.arg("-i");
         if let Some(from) = envelope.from() {
@@ -192,7 +225,7 @@ impl SendmailTransport {
     fn async_std_command(&self, envelope: &Envelope) -> async_std::process::Command {
         use async_std::process::Command;
 
-        let mut c = Command::new(&self.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");
@@ -214,6 +247,16 @@ impl Default for SendmailTransport {
     }
 }
 
+#[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;
@@ -235,7 +278,7 @@ impl Transport for SendmailTransport {
 
 #[cfg(feature = "async-std1")]
 #[async_trait]
-impl AsyncStd1Transport for SendmailTransport {
+impl AsyncTransport for AsyncSendmailTransport<AsyncStd1Executor> {
     type Ok = ();
     type Error = Error;
 
@@ -260,7 +303,7 @@ impl AsyncStd1Transport for SendmailTransport {
 
 #[cfg(feature = "tokio02")]
 #[async_trait]
-impl Tokio02Transport for SendmailTransport {
+impl AsyncTransport for AsyncSendmailTransport<Tokio02Executor> {
     type Ok = ();
     type Error = Error;
 
@@ -285,7 +328,7 @@ impl Tokio02Transport for SendmailTransport {
 
 #[cfg(feature = "tokio1")]
 #[async_trait]
-impl Tokio1Transport for SendmailTransport {
+impl AsyncTransport for AsyncSendmailTransport<Tokio1Executor> {
     type Ok = ();
     type Error = Error;
 

src/transport/smtp/async_transport.rs

@@ -1,28 +1,29 @@
+use std::marker::PhantomData;
+
 use async_trait::async_trait;
 
-#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
-use super::Tls;
 use super::{
     client::AsyncSmtpConnection, ClientId, Credentials, Error, Mechanism, Response, SmtpInfo,
 };
 #[cfg(feature = "async-std1")]
-use crate::AsyncStd1Transport;
-use crate::Envelope;
+use crate::AsyncStd1Executor;
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+use crate::AsyncTransport;
 #[cfg(feature = "tokio02")]
-use crate::Tokio02Transport;
+use crate::Tokio02Executor;
 #[cfg(feature = "tokio1")]
-use crate::Tokio1Transport;
+use crate::Tokio1Executor;
+use crate::{Envelope, Executor};
 
 #[allow(missing_debug_implementations)]
-#[derive(Clone)]
-pub struct AsyncSmtpTransport<C> {
+pub struct AsyncSmtpTransport<E> {
     // TODO: pool
-    inner: AsyncSmtpClient<C>,
+    inner: AsyncSmtpClient<E>,
 }
 
 #[cfg(feature = "tokio02")]
 #[async_trait]
-impl Tokio02Transport for AsyncSmtpTransport<Tokio02Connector> {
+impl AsyncTransport for AsyncSmtpTransport<Tokio02Executor> {
     type Ok = Response;
     type Error = Error;
 
@@ -40,7 +41,7 @@ impl Tokio02Transport for AsyncSmtpTransport<Tokio02Connector> {
 
 #[cfg(feature = "tokio1")]
 #[async_trait]
-impl Tokio1Transport for AsyncSmtpTransport<Tokio1Connector> {
+impl AsyncTransport for AsyncSmtpTransport<Tokio1Executor> {
     type Ok = Response;
     type Error = Error;
 
@@ -58,7 +59,7 @@ impl Tokio1Transport for AsyncSmtpTransport<Tokio1Connector> {
 
 #[cfg(feature = "async-std1")]
 #[async_trait]
-impl AsyncStd1Transport for AsyncSmtpTransport<AsyncStd1Connector> {
+impl AsyncTransport for AsyncSmtpTransport<AsyncStd1Executor> {
     type Ok = Response;
     type Error = Error;
 
@@ -74,9 +75,9 @@ impl AsyncStd1Transport for AsyncSmtpTransport<AsyncStd1Connector> {
     }
 }
 
-impl<C> AsyncSmtpTransport<C>
+impl<E> AsyncSmtpTransport<E>
 where
-    C: AsyncSmtpConnector,
+    E: Executor,
 {
     /// Simple and secure transport, using TLS connections to communicate with the SMTP server
     ///
@@ -93,7 +94,7 @@ where
         feature = "async-std1-rustls-tls"
     ))]
     pub fn relay(relay: &str) -> Result<AsyncSmtpTransportBuilder, Error> {
-        use super::{TlsParameters, SUBMISSIONS_PORT};
+        use super::{Tls, TlsParameters, SUBMISSIONS_PORT};
 
         let tls_parameters = TlsParameters::new(relay.into())?;
 
@@ -122,7 +123,7 @@ where
         feature = "async-std1-rustls-tls"
     ))]
     pub fn starttls_relay(relay: &str) -> Result<AsyncSmtpTransportBuilder, Error> {
-        use super::{TlsParameters, SUBMISSION_PORT};
+        use super::{Tls, TlsParameters, SUBMISSION_PORT};
 
         let tls_parameters = TlsParameters::new(relay.into())?;
 
@@ -134,7 +135,7 @@ where
     /// 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<C> {
+    pub fn unencrypted_localhost() -> AsyncSmtpTransport<E> {
         Self::builder_dangerous("localhost").build()
     }
 
@@ -158,6 +159,17 @@ where
     }
 }
 
+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)]
@@ -201,41 +213,39 @@ impl AsyncSmtpTransportBuilder {
         feature = "async-std1-native-tls",
         feature = "async-std1-rustls-tls"
     ))]
-    pub fn tls(mut self, tls: Tls) -> Self {
+    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<C>(self) -> AsyncSmtpTransport<C>
+    pub fn build<E>(self) -> AsyncSmtpTransport<E>
     where
-        C: AsyncSmtpConnector,
+        E: Executor,
     {
-        let connector = Default::default();
         let client = AsyncSmtpClient {
-            connector,
             info: self.info,
+            marker_: PhantomData,
         };
         AsyncSmtpTransport { inner: client }
     }
 }
 
 /// Build client
-#[derive(Clone)]
 pub struct AsyncSmtpClient<C> {
-    connector: C,
     info: SmtpInfo,
+    marker_: PhantomData<C>,
 }
 
-impl<C> AsyncSmtpClient<C>
+impl<E> AsyncSmtpClient<E>
 where
-    C: AsyncSmtpConnector,
+    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 = C::connect(
+        let mut conn = E::connect(
             &self.info.server,
             self.info.port,
             &self.info.hello_name,
@@ -250,152 +260,33 @@ where
     }
 }
 
-#[async_trait]
-pub trait AsyncSmtpConnector: Default + private::Sealed {
-    async fn connect(
-        hostname: &str,
-        port: u16,
-        hello_name: &ClientId,
-        tls: &Tls,
-    ) -> Result<AsyncSmtpConnection, Error>;
+impl<E> AsyncSmtpClient<E>
+where
+    E: Executor,
+{
+    fn clone(&self) -> Self {
+        Self {
+            info: self.info.clone(),
+            marker_: PhantomData,
+        }
+    }
 }
 
-#[derive(Debug, Copy, Clone, Default)]
+#[doc(hidden)]
+#[deprecated(note = "use lettre::Executor instead")]
+pub use crate::Executor as AsyncSmtpConnector;
+
+#[doc(hidden)]
+#[deprecated(note = "use lettre::Tokio02Executor instead")]
 #[cfg(feature = "tokio02")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tokio02")))]
-pub struct Tokio02Connector;
+pub type Tokio02Connector = crate::Tokio02Executor;
 
-#[async_trait]
-#[cfg(feature = "tokio02")]
-impl AsyncSmtpConnector for Tokio02Connector {
-    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)
-    }
-}
-
-#[derive(Debug, Copy, Clone, Default)]
+#[doc(hidden)]
+#[deprecated(note = "use lettre::Tokio1Executor instead")]
 #[cfg(feature = "tokio1")]
-#[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
-pub struct Tokio1Connector;
+pub type Tokio1Connector = crate::Tokio1Executor;
 
-#[async_trait]
-#[cfg(feature = "tokio1")]
-impl AsyncSmtpConnector for Tokio1Connector {
-    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)
-    }
-}
-
-#[derive(Debug, Copy, Clone, Default)]
+#[doc(hidden)]
+#[deprecated(note = "use lettre::AsyncStd1Executor instead")]
 #[cfg(feature = "async-std1")]
-#[cfg_attr(docsrs, doc(cfg(feature = "async-std1")))]
-pub struct AsyncStd1Connector;
-
-#[async_trait]
-#[cfg(feature = "async-std1")]
-impl AsyncSmtpConnector for AsyncStd1Connector {
-    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)
-    }
-}
-
-mod private {
-    use super::*;
-
-    pub trait Sealed {}
-
-    #[cfg(feature = "tokio02")]
-    impl Sealed for Tokio02Connector {}
-
-    #[cfg(feature = "tokio1")]
-    impl Sealed for Tokio1Connector {}
-
-    #[cfg(feature = "async-std1")]
-    impl Sealed for AsyncStd1Connector {}
-}
+pub type AsyncStd1Connector = crate::AsyncStd1Executor;

src/transport/smtp/authentication.rs

@@ -39,15 +39,16 @@ where
 #[derive(PartialEq, Eq, Copy, Clone, Hash, Debug)]
 #[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,
 }
 

src/transport/smtp/client/async_connection.rs

@@ -112,9 +112,32 @@ impl AsyncSmtpConnection {
         // Mail
         let mut mail_options = vec![];
 
-        if self.server_info().supports_feature(Extension::EightBitMime) {
+        // 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,

src/transport/smtp/client/async_net.rs

@@ -10,8 +10,10 @@ use std::{
     task::{Context, Poll},
 };
 
-use futures_io::{AsyncRead as FuturesAsyncRead, AsyncWrite as FuturesAsyncWrite};
-use futures_io::{Error as IoError, ErrorKind, Result as IoResult};
+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")]
@@ -370,8 +372,7 @@ impl AsyncNetworkStream {
 
                 #[cfg(feature = "async-std1-rustls-tls")]
                 return {
-                    use async_rustls::webpki::DNSNameRef;
-                    use async_rustls::TlsConnector;
+                    use async_rustls::{webpki::DNSNameRef, TlsConnector};
 
                     let domain = DNSNameRef::try_from_ascii_str(&domain)?;
 

src/transport/smtp/client/connection.rs

@@ -6,13 +6,15 @@ use std::{
 };
 
 use super::{ClientCodec, NetworkStream, TlsParameters};
-use crate::address::Envelope;
-use crate::transport::smtp::{
-    authentication::{Credentials, Mechanism},
-    commands::*,
-    error::Error,
-    extension::{ClientId, Extension, MailBodyParameter, MailParameter, ServerInfo},
-    response::{parse_response, Response},
+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")]
@@ -80,9 +82,32 @@ impl SmtpConnection {
         // Mail
         let mut mail_options = vec![];
 
-        if self.server_info().supports_feature(Extension::EightBitMime) {
+        // 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

src/transport/smtp/client/mod.rs

@@ -52,7 +52,7 @@ mod tls;
 /// The codec used for transparency
 #[derive(Default, Clone, Copy, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
-pub struct ClientCodec {
+struct ClientCodec {
     escape_count: u8,
 }
 

src/transport/smtp/client/tls.rs

@@ -65,7 +65,7 @@ impl TlsParametersBuilder {
     /// 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) -> &mut Self {
+    pub fn add_root_certificate(mut self, cert: Certificate) -> Self {
         self.root_certs.push(cert);
         self
     }
@@ -85,10 +85,7 @@ impl TlsParametersBuilder {
     /// 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,
-    ) -> &mut Self {
+    pub fn dangerous_accept_invalid_hostnames(mut self, accept_invalid_hostnames: bool) -> Self {
         self.accept_invalid_hostnames = accept_invalid_hostnames;
         self
     }
@@ -109,7 +106,7 @@ impl TlsParametersBuilder {
     ///
     /// 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) -> &mut Self {
+    pub fn dangerous_accept_invalid_certs(mut self, accept_invalid_certs: bool) -> Self {
         self.accept_invalid_certs = accept_invalid_certs;
         self
     }

src/transport/smtp/extension.rs

@@ -71,15 +71,15 @@ impl ClientId {
 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),

src/transport/smtp/mod.rs

@@ -43,8 +43,7 @@
 //!     .body(String::from("Be happy!"))?;
 //!
 //! // Create TLS transport on port 465
-//! let sender = SmtpTransport::relay("smtp.example.com")
-//!     .expect("relay valid")
+//! let sender = SmtpTransport::relay("smtp.example.com")?
 //!     .build();
 //! // Send the email via remote relay
 //! let result = sender.send(&email);
@@ -52,114 +51,71 @@
 //! # Ok(())
 //! # }
 //! ```
-
-//! #### Complete example
 //!
-//! ```todo
-//! # #[cfg(feature = "smtp-transport")]
-//! # {
-//! use lettre::transport::smtp::authentication::{Credentials, Mechanism};
-//! use lettre::{Email, Envelope, Transport, SmtpClient};
-//! use lettre::transport::smtp::extension::ClientId;
+//! #### Authentication
 //!
-//! let email_1 = Email::new(
-//!     Envelope::new(
-//!         Some(EmailAddress::new("user@localhost".to_string())?),
-//!         vec![EmailAddress::new("root@localhost".to_string())?],
-//!     )?,
-//!     "id1".to_string(),
-//!     "Hello world".to_string().into_bytes(),
-//! );
+//! Example with authentication and connection pool:
 //!
-//! let email_2 = Email::new(
-//!     Envelope::new(
-//!         Some(EmailAddress::new("user@localhost".to_string())?),
-//!         vec![EmailAddress::new("root@localhost".to_string())?],
-//!     )?,
-//!     "id2".to_string(),
-//!     "Hello world a second time".to_string().into_bytes(),
-//! );
+//! ```rust,no_run
+//! # #[cfg(all(feature = "builder", any(feature = "native-tls", feature = "rustls-tls")))]
+//! # fn test() -> Result<(), Box<dyn std::error::Error>> {
+//! use lettre::{Message, Transport, SmtpTransport, transport::smtp::{PoolConfig, authentication::{Credentials, Mechanism}}};
 //!
-//! // Connect to a remote server on a custom port
-//! let mut mailer = SmtpClient::new_simple("server.tld")?
-//!    // Set the name sent during EHLO/HELO, default is `localhost`
-//!    .hello_name(ClientId::Domain("my.hostname.tld".to_string()))
-//!    // Add credentials for authentication
-//!    .credentials(Credentials::new("username".to_string(), "password".to_string()))
-//!    // Enable SMTPUTF8 if the server supports it
-//!    .smtp_utf8(true)
-//!    // Configure expected authentication mechanism
-//!    .authentication_mechanism(Mechanism::Plain)
-//!    // Enable connection reuse
-//!    .connection_reuse(ConnectionReuseParameters::ReuseUnlimited).transport();
+//! 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_1 = mailer.send(&email_1);
-//! assert!(result_1.is_ok());
+//! // Create TLS transport on port 587 with STARTTLS
+//! let sender = SmtpTransport::starttls_relay("smtp.example.com")?
+//!     // Add credentials for authentication
+//!     .credentials(Credentials::new("username".to_string(), "password".to_string()))
+//!     // Configure expected authentication mechanism
+//!     .authentication(vec![Mechanism::Plain])
+//!     // Connection pool settings
+//!     .pool_config( PoolConfig::new().max_size(20))
+//!     .build();
 //!
-//! // The second email will use the same connection
-//! let result_2 = mailer.send(&email_2);
-//! assert!(result_2.is_ok());
-//!
-//! // Explicitly close the SMTP transaction as we enabled connection reuse
-//! mailer.close();
+//! // Send the email via remote relay
+//! let result = sender.send(&email);
+//! assert!(result.is_ok());
+//! # Ok(())
 //! # }
 //! ```
 //!
 //! You can specify custom TLS settings:
 //!
-//! ```todo
-//! # #[cfg(feature = "native-tls")]
-//! # {
-//! use lettre::{
-//!     ClientSecurity, ClientTlsParameters, EmailAddress, Envelope,
-//!     Email, SmtpClient, Transport,
-//! };
-//! use lettre::transport::smtp::authentication::{Credentials, Mechanism};
-//! use lettre::transport::smtp::ConnectionReuseParameters;
-//! use native_tls::{Protocol, TlsConnector};
+//! ```rust,no_run
+//! # #[cfg(all(feature = "builder", any(feature = "native-tls", feature = "rustls-tls")))]
+//! # fn test() -> Result<(), Box<dyn std::error::Error>> {
+//! use lettre::{Message, Transport, SmtpTransport, transport::smtp::client::{TlsParameters, Tls}};
 //!
-//!     let email = Email::new(
-//!         Envelope::new(
-//!             Some(EmailAddress::new("user@localhost".to_string())?),
-//!             vec![EmailAddress::new("root@localhost".to_string())?],
-//!         )?,
-//!         "message_id".to_string(),
-//!         "Hello world".to_string().into_bytes(),
-//!     );
+//! 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 mut tls_builder = TlsConnector::builder();
-//!     tls_builder.min_protocol_version(Some(Protocol::Tlsv10));
-//!     let tls_parameters =
-//!         ClientTlsParameters::new(
-//!             "smtp.example.com".to_string(),
-//!             tls_builder.build()?
-//!         );
+//! // Custom TLS configuration
+//! let tls = TlsParameters::builder("smtp.example.com".to_string())
+//!           .dangerous_accept_invalid_certs(true).build()?;
 //!
-//!     let mut mailer = SmtpClient::new(
-//!         ("smtp.example.com", 465), ClientSecurity::Wrapper(tls_parameters)
-//!     )?
-//!         .authentication_mechanism(Mechanism::Login)
-//!         .credentials(Credentials::new(
-//!             "example_username".to_string(), "example_password".to_string()
-//!         ))
-//!         .connection_reuse(ConnectionReuseParameters::ReuseUnlimited)
-//!         .transport();
+//! // Create TLS transport on port 465
+//! let sender = SmtpTransport::relay("smtp.example.com")?
+//!     // Custom TLS configuration
+//!     .tls(Tls::Required(tls))
+//!     .build();
 //!
-//!     let result = mailer.send(&email);
-//!
-//!     assert!(result.is_ok());
-//!
-//!     mailer.close();
+//! // Send the email via remote relay
+//! let result = sender.send(&email);
+//! assert!(result.is_ok());
+//! # Ok(())
 //! # }
 //! ```
-//!
 
-#[cfg(feature = "async-std1")]
-pub use self::async_transport::AsyncStd1Connector;
-#[cfg(feature = "tokio02")]
-pub use self::async_transport::Tokio02Connector;
-#[cfg(feature = "tokio1")]
-pub use self::async_transport::Tokio1Connector;
 #[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
 pub use self::async_transport::{
     AsyncSmtpConnector, AsyncSmtpTransport, AsyncSmtpTransportBuilder,
@@ -183,6 +139,19 @@ use crate::transport::smtp::{
 use client::Tls;
 use std::time::Duration;
 
+#[doc(hidden)]
+#[allow(deprecated)]
+#[cfg(feature = "async-std1")]
+pub use self::async_transport::AsyncStd1Connector;
+#[doc(hidden)]
+#[allow(deprecated)]
+#[cfg(feature = "tokio02")]
+pub use self::async_transport::Tokio02Connector;
+#[doc(hidden)]
+#[allow(deprecated)]
+#[cfg(feature = "tokio1")]
+pub use self::async_transport::Tokio1Connector;
+
 #[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
 mod async_transport;
 pub mod authentication;
@@ -206,7 +175,7 @@ pub const SMTP_PORT: u16 = 25;
 pub const SUBMISSION_PORT: u16 = 587;
 /// Default submission over TLS port
 ///
-/// https://tools.ietf.org/html/rfc8314
+/// Defined in [RFC8314](https://tools.ietf.org/html/rfc8314)
 pub const SUBMISSIONS_PORT: u16 = 465;
 
 /// Default timeout

src/transport/smtp/pool.rs

@@ -16,6 +16,11 @@ pub struct PoolConfig {
 }
 
 impl PoolConfig {
+    /// Create a new pool configuration with default values
+    pub fn new() -> Self {
+        Self::default()
+    }
+
     /// Minimum number of idle connections
     ///
     /// Defaults to `0`
@@ -28,7 +33,7 @@ impl PoolConfig {
     ///
     /// Defaults to `10`
     pub fn max_size(mut self, max_size: u32) -> Self {
-        self.min_idle = max_size;
+        self.max_size = max_size;
         self
     }
 

src/transport/smtp/transport.rs

@@ -8,11 +8,11 @@ use super::PoolConfig;
 use super::{ClientId, Credentials, Error, Mechanism, Response, SmtpConnection, SmtpInfo};
 #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
 use super::{Tls, TlsParameters, SUBMISSIONS_PORT, SUBMISSION_PORT};
-use crate::address::Envelope;
-use crate::Transport;
+use crate::{address::Envelope, Transport};
 
 #[allow(missing_debug_implementations)]
 #[derive(Clone)]
+/// Transport using the SMTP protocol
 pub struct SmtpTransport {
     #[cfg(feature = "r2d2")]
     inner: Pool<SmtpClient>,

src/transport/stub/mod.rs

@@ -9,8 +9,7 @@
 //! ```rust
 //! # #[cfg(feature = "builder")]
 //! # {
-//! use lettre::{Message, Transport};
-//! use lettre::transport::stub::StubTransport;
+//! use lettre::{transport::stub::StubTransport, Message, Transport};
 //!
 //! # use std::error::Error;
 //! # fn main() -> Result<(), Box<dyn Error>> {
@@ -29,13 +28,10 @@
 //! # }
 //! ```
 
-use crate::address::Envelope;
-#[cfg(feature = "async-std1")]
-use crate::AsyncStd1Transport;
-#[cfg(feature = "tokio02")]
-use crate::Tokio02Transport;
-use crate::Transport;
-#[cfg(any(feature = "async-std1", feature = "tokio02"))]
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
+use crate::AsyncTransport;
+use crate::{address::Envelope, Transport};
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
 use async_trait::async_trait;
 use std::{error::Error as StdError, fmt};
 
@@ -84,20 +80,9 @@ impl Transport for StubTransport {
     }
 }
 
-#[cfg(feature = "async-std1")]
+#[cfg(any(feature = "tokio02", feature = "tokio1", feature = "async-std1"))]
 #[async_trait]
-impl AsyncStd1Transport for StubTransport {
-    type Ok = ();
-    type Error = Error;
-
-    async fn send_raw(&self, _envelope: &Envelope, _email: &[u8]) -> Result<Self::Ok, Self::Error> {
-        self.response
-    }
-}
-
-#[cfg(feature = "tokio02")]
-#[async_trait]
-impl Tokio02Transport for StubTransport {
+impl AsyncTransport for StubTransport {
     type Ok = ();
     type Error = Error;
 

tests/transport_file.rs

@@ -81,21 +81,27 @@ mod test {
                 "Be happy!"
             )
         );
-        remove_file(eml_file).unwrap();
 
         assert_eq!(
             json,
             "{\"forward_path\":[\"hei@domain.tld\"],\"reverse_path\":\"nobody@domain.tld\"}"
         );
+
+        let (e, m) = sender.read(&id).unwrap();
+
+        assert_eq!(&e, email.envelope());
+        assert_eq!(m, email.formatted());
+
+        remove_file(eml_file).unwrap();
         remove_file(json_file).unwrap();
     }
 
     #[cfg(feature = "async-std1")]
     #[async_std::test]
     async fn file_transport_asyncstd1() {
-        use lettre::AsyncStd1Transport;
+        use lettre::{AsyncFileTransport, AsyncStd1Executor, AsyncTransport};
 
-        let sender = FileTransport::new(temp_dir());
+        let sender = AsyncFileTransport::<AsyncStd1Executor>::new(temp_dir());
         let email = Message::builder()
             .from("NoBody <nobody@domain.tld>".parse().unwrap())
             .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
@@ -130,9 +136,9 @@ mod test {
     #[cfg(feature = "tokio02")]
     #[tokio::test]
     async fn file_transport_tokio02() {
-        use lettre::Tokio02Transport;
+        use lettre::{AsyncFileTransport, AsyncTransport, Tokio02Executor};
 
-        let sender = FileTransport::new(temp_dir());
+        let sender = AsyncFileTransport::<Tokio02Executor>::new(temp_dir());
         let email = Message::builder()
             .from("NoBody <nobody@domain.tld>".parse().unwrap())
             .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())

tests/transport_sendmail.rs

@@ -26,9 +26,9 @@ mod test {
     #[cfg(feature = "async-std1")]
     #[async_std::test]
     async fn sendmail_transport_asyncstd1() {
-        use lettre::AsyncStd1Transport;
+        use lettre::{AsyncSendmailTransport, AsyncStd1Executor, AsyncTransport};
 
-        let sender = SendmailTransport::new();
+        let sender = AsyncSendmailTransport::<AsyncStd1Executor>::new();
         let email = Message::builder()
             .from("NoBody <nobody@domain.tld>".parse().unwrap())
             .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
@@ -46,9 +46,9 @@ mod test {
     #[cfg(feature = "tokio02")]
     #[tokio::test]
     async fn sendmail_transport_tokio02() {
-        use lettre::Tokio02Transport;
+        use lettre::{AsyncSendmailTransport, Tokio02Executor, Tokio02Transport};
 
-        let sender = SendmailTransport::new();
+        let sender = AsyncSendmailTransport::<Tokio02Executor>::new();
         let email = Message::builder()
             .from("NoBody <nobody@domain.tld>".parse().unwrap())
             .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())

tests/transport_smtp_pool.rs

@@ -1,7 +1,6 @@
 #[cfg(all(test, feature = "smtp-transport", feature = "r2d2"))]
 mod test {
-    use lettre::address::Envelope;
-    use lettre::{SmtpTransport, Transport};
+    use lettre::{address::Envelope, SmtpTransport, Transport};
 
     use std::{sync::mpsc, thread};