regression

fix
clippy
2025-06-02 11:40:45 +02:00 · 2025-06-02 11:14:11 +02:00 · 2025-06-02 11:09:21 +02:00 · 2025-06-02 11:05:59 +02:00 · 2025-06-02 10:43:17 +02:00 · 2025-05-24 16:37:54 +02:00
32 changed files with 1905 additions and 809 deletions
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -75,8 +75,8 @@ jobs:
            rust: stable
          - name: beta
            rust: beta
-          - name: '1.71'
-            rust: '1.71'
+          - name: '1.74'
+            rust: '1.74'

    steps:
      - name: Checkout
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,67 @@
+<a name="v0.11.16"></a>
+### v0.11.16 (2025-05-12)
+
+#### Features
+
+* Always implement `Clone` for `AsyncFileTransport` ([#1075])
+
+#### Changes
+
+* `Tls`, `CertificateStore`, `TlsParameters`, `TlsParametersBuilder`, `Certificate` and `Identity`
+  are now marked as deprecated when no TLS backend is enabled. They will be properly feature gated
+  in lettre v0.12 ([#1084])
+
+#### Misc
+
+* Gate `web-time` behind `cfg(target_arch = "wasm32")]` ([#1086])
+* Add missing `#[doc(cfg(...))]` attributes ([#1086])
+* Upgrade `webpki-roots` to v1 ([#1088])
+* Cleanup internal `TlsParameters` and `(Async)NetworkStream` structures ([#1082])
+* Feature gate internal `TransportBuilder::tls` to avoid recursive call site warnings ([#1083])
+* Fix workaround for embedding cargo script in rustdoc output ([#1077])
+* Fix `clippy::io_other_error` warnings ([#1078])
+* Upgrade semver compatible dependencies ([#1076], [#1079], [#1080])
+
+[#1075]: https://github.com/lettre/lettre/pull/1075
+[#1076]: https://github.com/lettre/lettre/pull/1076
+[#1077]: https://github.com/lettre/lettre/pull/1077
+[#1078]: https://github.com/lettre/lettre/pull/1078
+[#1079]: https://github.com/lettre/lettre/pull/1079
+[#1080]: https://github.com/lettre/lettre/pull/1080
+[#1082]: https://github.com/lettre/lettre/pull/1082
+[#1083]: https://github.com/lettre/lettre/pull/1083
+[#1084]: https://github.com/lettre/lettre/pull/1084
+[#1086]: https://github.com/lettre/lettre/pull/1086
+[#1088]: https://github.com/lettre/lettre/pull/1088
+
+<a name="v0.11.15"></a>
+### v0.11.15 (2025-03-10)
+
+#### Upgrade notes
+
+* MSRV is now 1.74 ([#1060])
+
+#### Features
+
+* Add controlled shutdown methods ([#1045], [#1068])
+
+#### Misc
+
+* Deny `unreachable_pub` lint ([#1058])
+* Bump minimum supported `rustls` ([#1063])
+* Bump minimum supported `serde` ([#1064])
+* Upgrade semver compatible dependencies ([#1067])
+* Upgrade `email-encoding` to v0.4 ([#1069])
+
+[#1045]: https://github.com/lettre/lettre/pull/1045
+[#1058]: https://github.com/lettre/lettre/pull/1058
+[#1060]: https://github.com/lettre/lettre/pull/1060
+[#1063]: https://github.com/lettre/lettre/pull/1063
+[#1064]: https://github.com/lettre/lettre/pull/1064
+[#1067]: https://github.com/lettre/lettre/pull/1067
+[#1068]: https://github.com/lettre/lettre/pull/1068
+[#1069]: https://github.com/lettre/lettre/pull/1069
+
 <a name="v0.11.14"></a>
 ### v0.11.14 (2025-02-23)

--- a/Cargo.lock
+++ b/Cargo.lock
--- a/Cargo.toml
+++ b/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 = "0.11.14"
+version = "0.11.16"
 description = "Email client"
 readme = "README.md"
 homepage = "https://lettre.rs"
@@ -11,7 +11,7 @@ authors = ["Alexis Mousset <contact@amousset.me>", "Paolo Barbolini <paolo@paolo
 categories = ["email", "network-programming"]
 keywords = ["email", "smtp", "mailer", "message", "sendmail"]
 edition = "2021"
-rust-version = "1.71"
+rust-version = "1.74"

 [badges]
 is-it-maintained-issue-resolution = { repository = "lettre/lettre" }
@@ -32,11 +32,11 @@ mime = { version = "0.3.4", optional = true }
 fastrand = { version = "2.0", optional = true }
 quoted_printable = { version = "0.5", optional = true }
 base64 = { version = "0.22", optional = true }
-email-encoding = { version = "0.3", optional = true }
+email-encoding = { version = "0.4", optional = true }

 # file transport
 uuid = { version = "1", features = ["v4"], optional = true }
-serde = { version = "1", features = ["derive"], optional = true }
+serde = { version = "1.0.110", features = ["derive"], optional = true }
 serde_json = { version = "1", optional = true }

 # smtp-transport
@@ -48,9 +48,10 @@ percent-encoding = { version = "2.3", optional = true }

 ## tls
 native-tls = { version = "0.2.9", optional = true } # feature
-rustls = { version = "0.23.5", default-features = false, features = ["logging", "std", "tls12"], optional = true }
+rustls = { version = "0.23.18", default-features = false, features = ["logging", "std", "tls12"], optional = true }
+rustls-platform-verifier = { version = "0.6.0", optional = true }
 rustls-native-certs = { version = "0.8", optional = true }
-webpki-roots = { version = "0.26", optional = true }
+webpki-roots = { version = "1.0.0", optional = true }
 boring = { version = "4", optional = true }

 # async
@@ -73,6 +74,7 @@ sha2 = { version = "0.10", features = ["oid"], optional = true }
 rsa = { version = "0.9", optional = true }
 ed25519-dalek = { version = "2", optional = true }

+[target.'cfg(target_arch = "wasm32")'.dependencies]
 ## web-time for wasm support
 web-time = { version = "1.1.0", optional = true }

--- a/README.md
+++ b/README.md
@@ -28,8 +28,8 @@
 </div>

 <div align="center">
-  <a href="https://deps.rs/crate/lettre/0.11.14">
-    <img src="https://deps.rs/crate/lettre/0.11.14/status.svg"
+  <a href="https://deps.rs/crate/lettre/0.11.16">
+    <img src="https://deps.rs/crate/lettre/0.11.16/status.svg"
      alt="dependency status" />
  </a>
 </div>
@@ -53,12 +53,12 @@ Lettre does not provide (for now):
 ## Supported Rust Versions

 Lettre supports all Rust versions released in the last 6 months. At the time of writing
-the minimum supported Rust version is 1.71, but this could change at any time either from
+the minimum supported Rust version is 1.74, but this could change at any time either from
 one of our dependencies bumping their MSRV or by a new patch release of lettre.

 ## Example

-This library requires Rust 1.71 or newer.
+This library requires Rust 1.74 or newer.
 To use this library, add the following to your `Cargo.toml`:

 ```toml
@@ -73,9 +73,9 @@ use lettre::{Message, SmtpTransport, Transport};

 fn main() {
    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())
+        .from(Mailbox::new("NoBody".to_owned(), "nobody@domain.tld".parse().unwrap()))
+        .reply_to(Mailbox::new("Yuin".to_owned(), "yuin@domain.tld".parse().unwrap()))
+        .to(Mailbox::new("Hei".to_owned(), "hei@domain.tld".parse().unwrap()))
        .subject("Happy new year")
        .header(ContentType::TEXT_PLAIN)
        .body(String::from("Be happy!"))
--- a/src/address/envelope.rs
+++ b/src/address/envelope.rs
@@ -53,7 +53,7 @@ mod serde_forward_path {
            }
        }
    }
-    pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<Address>, D::Error>
+    pub(super) fn deserialize<'de, D>(deserializer: D) -> Result<Vec<Address>, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
@@ -163,6 +163,7 @@ impl Envelope {
 }

 #[cfg(feature = "builder")]
+#[cfg_attr(docsrs, doc(cfg(feature = "builder")))]
 impl TryFrom<&Headers> for Envelope {
    type Error = Error;

--- a/src/executor.rs
+++ b/src/executor.rs
@@ -45,6 +45,7 @@ use crate::transport::smtp::Error;
 #[async_trait]
 pub trait Executor: Debug + Send + Sync + 'static + private::Sealed {
    #[cfg(feature = "smtp-transport")]
+    #[allow(private_bounds)]
    type Handle: SpawnHandle;
    #[cfg(feature = "smtp-transport")]
    type Sleep: Future<Output = ()> + Send + 'static;
@@ -82,8 +83,8 @@ pub trait Executor: Debug + Send + Sync + 'static + private::Sealed {
 #[doc(hidden)]
 #[cfg(feature = "smtp-transport")]
 #[async_trait]
-pub trait SpawnHandle: Debug + Send + Sync + 'static + private::Sealed {
-    async fn shutdown(self);
+pub(crate) trait SpawnHandle: Debug + Send + Sync + 'static + private::Sealed {
+    async fn shutdown(&self);
 }

 /// Async [`Executor`] using `tokio` `1.x`
@@ -177,7 +178,7 @@ impl Executor for Tokio1Executor {
 #[cfg(all(feature = "smtp-transport", feature = "tokio1"))]
 #[async_trait]
 impl SpawnHandle for tokio1_crate::task::JoinHandle<()> {
-    async fn shutdown(self) {
+    async fn shutdown(&self) {
        self.abort();
    }
 }
@@ -201,7 +202,7 @@ pub struct AsyncStd1Executor;
 #[cfg(feature = "async-std1")]
 impl Executor for AsyncStd1Executor {
    #[cfg(feature = "smtp-transport")]
-    type Handle = async_std::task::JoinHandle<()>;
+    type Handle = futures_util::future::AbortHandle;
    #[cfg(feature = "smtp-transport")]
    type Sleep = BoxFuture<'static, ()>;

@@ -211,7 +212,9 @@ impl Executor for AsyncStd1Executor {
        F: Future<Output = ()> + Send + 'static,
        F::Output: Send + 'static,
    {
-        async_std::task::spawn(fut)
+        let (handle, registration) = futures_util::future::AbortHandle::new_pair();
+        async_std::task::spawn(futures_util::future::Abortable::new(fut, registration));
+        handle
    }

    #[cfg(feature = "smtp-transport")]
@@ -272,9 +275,9 @@ impl Executor for AsyncStd1Executor {

 #[cfg(all(feature = "smtp-transport", feature = "async-std1"))]
 #[async_trait]
-impl SpawnHandle for async_std::task::JoinHandle<()> {
-    async fn shutdown(self) {
-        self.cancel().await;
+impl SpawnHandle for futures_util::future::AbortHandle {
+    async fn shutdown(&self) {
+        self.abort();
    }
 }

@@ -291,5 +294,5 @@ mod private {
    impl Sealed for tokio1_crate::task::JoinHandle<()> {}

    #[cfg(all(feature = "smtp-transport", feature = "async-std1"))]
-    impl Sealed for async_std::task::JoinHandle<()> {}
+    impl Sealed for futures_util::future::AbortHandle {}
 }
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,7 +6,7 @@
 //! * Secure defaults
 //! * Async support
 //!
-//! Lettre requires Rust 1.71 or newer.
+//! Lettre requires Rust 1.74 or newer.
 //!
 //! ## Features
 //!
@@ -93,17 +93,20 @@
 //! When the `rustls` feature is enabled, one of the following verification backends
 //! MUST also be enabled.
 //!
-//! * **rustls-native-certs**: verify TLS certificates using the platform's native certificate store (see [`rustls-native-certs`])
+//! * **rustls-platform-verifier**: verify TLS certificate using the OS's native certificate store (see [`rustls-platform-verifier`])
+//! * **rustls-native-certs**: verify TLS certificates using the platform's native certificate store (see [`rustls-native-certs`]) - when in doubt use `rustls-platform-verifier`
 //! * **webpki-roots**: verify TLS certificates against Mozilla's root certificates (see [`webpki-roots`])
 //!
-//! For the `rustls-native-certs` backend to work correctly, the following packages
-//! will need to be installed in order for the build stage and the compiled program
-//! to run properly.
+//! The following packages will need to be installed in order for the build
+//! stage and the compiled program to run properly.
 //!
-//! | Distro       | Build-time packages        | Runtime packages             |
-//! | ------------ | -------------------------- | ---------------------------- |
-//! | Debian       | none                       | `ca-certificates`            |
-//! | Alpine Linux | none                       | `ca-certificates`            |
+//! | Verification backend       | Distro       | Build-time packages        | Runtime packages             |
+//! | ---------------------      | ------------ | -------------------------- | ---------------------------- |
+//! | `rustls-platform-verifier` | Debian       | none                       | `ca-certificates`            |
+//! | `rustls-platform-verifier` | Alpine Linux | none                       | `ca-certificates`            |
+//! | `rustls-native-certs`      | Debian       | none                       | `ca-certificates`            |
+//! | `rustls-native-certs`      | Alpine Linux | none                       | `ca-certificates`            |
+//! | `webpki-roots`             | any          | none                       | none                         |
 //!
 //! ### Sendmail transport
 //!
@@ -151,6 +154,7 @@
 //! [AWS-LC]: https://github.com/aws/aws-lc
 //! [`aws-lc-rs`]: https://crates.io/crates/aws-lc-rs
 //! [`ring`]: https://crates.io/crates/ring
+//! [`rustls-platform-verifier`]: https://crates.io/crates/rustls-platform-verifier
 //! [`rustls-native-certs`]: https://crates.io/crates/rustls-native-certs
 //! [`webpki-roots`]: https://crates.io/crates/webpki-roots
 //! [Tokio 1.x]: https://docs.rs/tokio/1
@@ -158,11 +162,12 @@
 //! [mime 0.3]: https://docs.rs/mime/0.3
 //! [DKIM]: https://datatracker.ietf.org/doc/html/rfc6376

-#![doc(html_root_url = "https://docs.rs/crate/lettre/0.11.14")]
+#![doc(html_root_url = "https://docs.rs/crate/lettre/0.11.16")]
 #![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(
+    unreachable_pub,
    missing_copy_implementations,
    trivial_casts,
    trivial_numeric_casts,
@@ -207,12 +212,13 @@ mod compiletime_checks {

    #[cfg(all(
        feature = "rustls",
+        not(feature = "rustls-platform-verifier"),
        not(feature = "rustls-native-certs"),
        not(feature = "webpki-roots")
    ))]
    compile_error!(
-        "feature `rustls` also requires either the `rustls-native-certs` or the `webpki-roots` feature to
-    be enabled"
+        "feature `rustls` also requires either the `rustls-platform-verifier`, the `rustls-native-certs`
+    or the `webpki-roots` feature to be enabled"
    );

    #[cfg(all(feature = "native-tls", feature = "boring-tls"))]
--- a/src/message/mailbox/parsers/rfc2822.rs
+++ b/src/message/mailbox/parsers/rfc2822.rs
@@ -41,14 +41,14 @@ fn quoted_pair() -> impl Parser<char, char, Error = Cheap<char>> {

 // FWS             =       ([*WSP CRLF] 1*WSP) /   ; Folding white space
 //                         obs-FWS
-pub fn fws() -> impl Parser<char, Option<char>, Error = Cheap<char>> {
+pub(super) fn fws() -> impl Parser<char, Option<char>, Error = Cheap<char>> {
    rfc2234::wsp()
        .or_not()
        .then_ignore(rfc2234::wsp().ignored().repeated())
 }

 // CFWS            =       *([FWS] comment) (([FWS] comment) / FWS)
-pub fn cfws() -> impl Parser<char, Option<char>, Error = Cheap<char>> {
+pub(super) fn cfws() -> impl Parser<char, Option<char>, Error = Cheap<char>> {
    // TODO: comment are not currently supported, so for now a cfws is
    // the same as a fws.
    fws()
@@ -106,12 +106,12 @@ pub(super) fn atom() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
 }

 // dot-atom        =       [CFWS] dot-atom-text [CFWS]
-pub fn dot_atom() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
+pub(super) fn dot_atom() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
    cfws().chain(dot_atom_text())
 }

 // dot-atom-text   =       1*atext *("." 1*atext)
-pub fn dot_atom_text() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
+pub(super) fn dot_atom_text() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
    atext().repeated().at_least(1).chain(
        just('.')
            .chain(atext().repeated().at_least(1))
@@ -204,7 +204,7 @@ pub(crate) fn mailbox_list(
 // https://datatracker.ietf.org/doc/html/rfc2822#section-3.4.1

 // addr-spec       =       local-part "@" domain
-pub fn addr_spec() -> impl Parser<char, (String, String), Error = Cheap<char>> {
+pub(super) fn addr_spec() -> impl Parser<char, (String, String), Error = Cheap<char>> {
    local_part()
        .collect()
        .then_ignore(just('@'))
@@ -212,12 +212,12 @@ pub fn addr_spec() -> impl Parser<char, (String, String), Error = Cheap<char>> {
 }

 // local-part      =       dot-atom / quoted-string / obs-local-part
-pub fn local_part() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
+pub(super) fn local_part() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
    choice((dot_atom(), quoted_string(), obs_local_part()))
 }

 // domain          =       dot-atom / domain-literal / obs-domain
-pub fn domain() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
+pub(super) fn domain() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
    // NOTE: omitting domain-literal since it may never be used
    choice((dot_atom(), obs_domain()))
 }
@@ -240,11 +240,11 @@ fn obs_phrase() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
 // https://datatracker.ietf.org/doc/html/rfc2822#section-4.4

 // obs-local-part  =       word *("." word)
-pub fn obs_local_part() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
+pub(super) fn obs_local_part() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
    word().chain(just('.').chain(word()).repeated().flatten())
 }

 // obs-domain      =       atom *("." atom)
-pub fn obs_domain() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
+pub(super) fn obs_domain() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
    atom().chain(just('.').chain(atom()).repeated().flatten())
 }
--- a/src/time.rs
+++ b/src/time.rs
@@ -1,6 +1,6 @@
 use std::time::SystemTime;

-#[cfg(feature = "web")]
+#[cfg(all(feature = "web", target_arch = "wasm32"))]
 pub(crate) fn now() -> SystemTime {
    fn to_std_systemtime(time: web_time::SystemTime) -> std::time::SystemTime {
        let duration = time
@@ -18,7 +18,7 @@ pub(crate) fn now() -> SystemTime {
    to_std_systemtime(web_time::SystemTime::now())
 }

-#[cfg(not(feature = "web"))]
+#[cfg(not(all(feature = "web", target_arch = "wasm32")))]
 pub(crate) fn now() -> SystemTime {
    // FIXME: change to #[expect(clippy::disallowed_methods, reason = "the `web` feature is disabled")]
    #[allow(clippy::disallowed_methods)]
--- a/src/transport/file/error.rs
+++ b/src/transport/file/error.rs
@@ -34,6 +34,7 @@ impl Error {

    /// Returns true if the error is an envelope serialization or deserialization error
    #[cfg(feature = "file-transport-envelope")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "file-transport-envelope")))]
    pub fn is_envelope(&self) -> bool {
        matches!(self.inner.kind, Kind::Envelope)
    }
--- a/src/transport/file/mod.rs
+++ b/src/transport/file/mod.rs
@@ -173,7 +173,7 @@ pub struct FileTransport {
 }

 /// Asynchronously writes the content and the envelope information to a file
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(docsrs, doc(cfg(any(feature = "tokio1", feature = "async-std1"))))]
 #[cfg(any(feature = "async-std1", feature = "tokio1"))]
@@ -199,6 +199,7 @@ impl FileTransport {
    /// Writes the email content in eml format and the envelope
    /// in json format.
    #[cfg(feature = "file-transport-envelope")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "file-transport-envelope")))]
    pub fn with_envelope<P: AsRef<Path>>(path: P) -> FileTransport {
        FileTransport {
            path: PathBuf::from(path.as_ref()),
@@ -211,6 +212,7 @@ impl FileTransport {
    ///
    /// Reads the envelope and the raw message content.
    #[cfg(feature = "file-transport-envelope")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "file-transport-envelope")))]
    pub fn read(&self, email_id: &str) -> Result<(Envelope, Vec<u8>), Error> {
        use std::fs;

@@ -249,6 +251,7 @@ where
    /// Writes the email content in eml format and the envelope
    /// in json format.
    #[cfg(feature = "file-transport-envelope")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "file-transport-envelope")))]
    pub fn with_envelope<P: AsRef<Path>>(path: P) -> Self {
        Self {
            inner: FileTransport::with_envelope(path),
@@ -260,6 +263,7 @@ where
    ///
    /// Reads the envelope and the raw message content.
    #[cfg(feature = "file-transport-envelope")]
+    #[cfg_attr(docsrs, doc(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!("{email_id}.eml"));
        let eml = E::fs_read(&eml_file).await.map_err(error::io)?;
@@ -272,6 +276,16 @@ where
    }
 }

+#[cfg(any(feature = "async-std1", feature = "tokio1"))]
+impl<E: Executor> Clone for AsyncFileTransport<E> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+            marker_: PhantomData,
+        }
+    }
+}
+
 impl Transport for FileTransport {
    type Ok = Id;
    type Error = Error;
--- a/src/transport/mod.rs
+++ b/src/transport/mod.rs
@@ -140,6 +140,10 @@ pub trait Transport {
    }

    fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error>;
+
+    /// Shuts down the transport. Future calls to [`Self::send`] and
+    /// [`Self::send_raw`] might fail.
+    fn shutdown(&self) {}
 }

 /// Async Transport method for emails
@@ -166,4 +170,8 @@ pub trait AsyncTransport {
    }

    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error>;
+
+    /// Shuts down the transport. Future calls to [`Self::send`] and
+    /// [`Self::send_raw`] might fail.
+    async fn shutdown(&self) {}
 }
--- a/src/transport/smtp/async_transport.rs
+++ b/src/transport/smtp/async_transport.rs
@@ -79,6 +79,11 @@ impl AsyncTransport for AsyncSmtpTransport<Tokio1Executor> {

        Ok(result)
    }
+
+    async fn shutdown(&self) {
+        #[cfg(feature = "pool")]
+        self.inner.shutdown().await;
+    }
 }

 #[cfg(feature = "async-std1")]
@@ -97,6 +102,11 @@ impl AsyncTransport for AsyncSmtpTransport<AsyncStd1Executor> {

        Ok(result)
    }
+
+    async fn shutdown(&self) {
+        #[cfg(feature = "pool")]
+        self.inner.shutdown().await;
+    }
 }

 impl<E> AsyncSmtpTransport<E>
@@ -224,7 +234,7 @@ where
    /// a proper URL encoder, like the following cargo script:
    ///
    /// ```rust
-    /// # let _ = r#"
+    /// # const TOML: &str = r#"
    /// #!/usr/bin/env cargo
    ///
    /// //! ```cargo
@@ -460,7 +470,7 @@ impl AsyncSmtpTransportBuilder {
 }

 /// Build client
-pub struct AsyncSmtpClient<E> {
+pub(super) struct AsyncSmtpClient<E> {
    info: SmtpInfo,
    marker_: PhantomData<E>,
 }
@@ -472,7 +482,7 @@ where
    /// Creates a new connection directly usable to send emails
    ///
    /// Handles encryption and authentication
-    pub async fn connection(&self) -> Result<AsyncSmtpConnection, Error> {
+    pub(super) async fn connection(&self) -> Result<AsyncSmtpConnection, Error> {
        let mut conn = E::connect(
            &self.info.server,
            self.info.port,
--- a/src/transport/smtp/client/async_connection.rs
+++ b/src/transport/smtp/client/async_connection.rs
@@ -54,6 +54,7 @@ impl AsyncSmtpConnection {
    ///
    /// Sends EHLO and parses server information
    #[cfg(feature = "tokio1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
    pub async fn connect_with_transport(
        stream: Box<dyn AsyncTokioStream>,
        hello_name: &ClientId,
@@ -94,6 +95,7 @@ impl AsyncSmtpConnection {
    /// # }
    /// ```
    #[cfg(feature = "tokio1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
    pub async fn connect_tokio1<T: tokio1_crate::net::ToSocketAddrs>(
        server: T,
        timeout: Option<Duration>,
@@ -112,6 +114,7 @@ impl AsyncSmtpConnection {
    ///
    /// Sends EHLO and parses server information
    #[cfg(feature = "async-std1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async-std1")))]
    pub async fn connect_asyncstd1<T: async_std::net::ToSocketAddrs>(
        server: T,
        timeout: Option<Duration>,
@@ -376,6 +379,10 @@ impl AsyncSmtpConnection {

    /// The X509 certificate of the server (DER encoded)
    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+    )]
    pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
        self.stream.get_ref().peer_certificate()
    }
@@ -392,12 +399,14 @@ impl AsyncSmtpConnection {
    /// as the TLSA records match the leaf or issuer certificates.
    /// It cannot be called on non Boring TLS streams.
    #[cfg(feature = "boring-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
    pub fn tls_verify_result(&self) -> Result<(), Error> {
        self.stream.get_ref().tls_verify_result()
    }

    /// All the X509 certificates of the chain (DER encoded)
    #[cfg(any(feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "rustls", feature = "boring-tls"))))]
    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
        self.stream.get_ref().certificate_chain()
    }
--- a/src/transport/smtp/client/async_net.rs
+++ b/src/transport/smtp/client/async_net.rs
@@ -9,13 +9,11 @@ use std::{
 #[cfg(feature = "async-std1")]
 use async_std::net::{TcpStream as AsyncStd1TcpStream, ToSocketAddrs as AsyncStd1ToSocketAddrs};
 use futures_io::{
-    AsyncRead as FuturesAsyncRead, AsyncWrite as FuturesAsyncWrite, Error as IoError, ErrorKind,
+    AsyncRead as FuturesAsyncRead, AsyncWrite as FuturesAsyncWrite, Error as IoError,
    Result as IoResult,
 };
 #[cfg(feature = "async-std1-rustls")]
-use futures_rustls::client::TlsStream as AsyncStd1RustlsTlsStream;
-#[cfg(any(feature = "tokio1-rustls", feature = "async-std1-rustls"))]
-use rustls::pki_types::ServerName;
+use futures_rustls::client::TlsStream as AsyncStd1RustlsStream;
 #[cfg(feature = "tokio1-boring-tls")]
 use tokio1_boring::SslStream as Tokio1SslStream;
 #[cfg(feature = "tokio1")]
@@ -28,7 +26,7 @@ use tokio1_crate::net::{
 #[cfg(feature = "tokio1-native-tls")]
 use tokio1_native_tls_crate::TlsStream as Tokio1TlsStream;
 #[cfg(feature = "tokio1-rustls")]
-use tokio1_rustls::client::TlsStream as Tokio1RustlsTlsStream;
+use tokio1_rustls::client::TlsStream as Tokio1RustlsStream;

 #[cfg(any(
    feature = "tokio1-native-tls",
@@ -79,7 +77,7 @@ enum InnerAsyncNetworkStream {
    Tokio1NativeTls(Tokio1TlsStream<Box<dyn AsyncTokioStream>>),
    /// Encrypted Tokio 1.x TCP stream
    #[cfg(feature = "tokio1-rustls")]
-    Tokio1RustlsTls(Tokio1RustlsTlsStream<Box<dyn AsyncTokioStream>>),
+    Tokio1Rustls(Tokio1RustlsStream<Box<dyn AsyncTokioStream>>),
    /// Encrypted Tokio 1.x TCP stream
    #[cfg(feature = "tokio1-boring-tls")]
    Tokio1BoringTls(Tokio1SslStream<Box<dyn AsyncTokioStream>>),
@@ -88,7 +86,7 @@ enum InnerAsyncNetworkStream {
    AsyncStd1Tcp(AsyncStd1TcpStream),
    /// Encrypted Tokio 1.x TCP stream
    #[cfg(feature = "async-std1-rustls")]
-    AsyncStd1RustlsTls(AsyncStd1RustlsTlsStream<AsyncStd1TcpStream>),
+    AsyncStd1Rustls(AsyncStd1RustlsStream<AsyncStd1TcpStream>),
    /// Can't be built
    None,
 }
@@ -113,17 +111,16 @@ impl AsyncNetworkStream {
                s.get_ref().get_ref().get_ref().peer_addr()
            }
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => s.get_ref().0.peer_addr(),
+            InnerAsyncNetworkStream::Tokio1Rustls(s) => s.get_ref().0.peer_addr(),
            #[cfg(feature = "tokio1-boring-tls")]
            InnerAsyncNetworkStream::Tokio1BoringTls(s) => s.get_ref().peer_addr(),
            #[cfg(feature = "async-std1")]
            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => s.peer_addr(),
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => s.get_ref().0.peer_addr(),
+            InnerAsyncNetworkStream::AsyncStd1Rustls(s) => s.get_ref().0.peer_addr(),
            InnerAsyncNetworkStream::None => {
                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
-                Err(IoError::new(
-                    ErrorKind::Other,
+                Err(IoError::other(
                    "InnerAsyncNetworkStream::None must never be built",
                ))
            }
@@ -131,11 +128,13 @@ impl AsyncNetworkStream {
    }

    #[cfg(feature = "tokio1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
    pub fn use_existing_tokio1(stream: Box<dyn AsyncTokioStream>) -> AsyncNetworkStream {
        AsyncNetworkStream::new(InnerAsyncNetworkStream::Tokio1Tcp(stream))
    }

    #[cfg(feature = "tokio1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "tokio1")))]
    pub async fn connect_tokio1<T: Tokio1ToSocketAddrs>(
        server: T,
        timeout: Option<Duration>,
@@ -202,6 +201,7 @@ impl AsyncNetworkStream {
    }

    #[cfg(feature = "async-std1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async-std1")))]
    pub async fn connect_asyncstd1<T: AsyncStd1ToSocketAddrs>(
        server: T,
        timeout: Option<Duration>,
@@ -317,11 +317,9 @@ impl AsyncNetworkStream {
        tcp_stream: Box<dyn AsyncTokioStream>,
        tls_parameters: TlsParameters,
    ) -> Result<InnerAsyncNetworkStream, Error> {
-        let domain = tls_parameters.domain().to_owned();
-
-        match tls_parameters.connector {
+        match tls_parameters.inner {
            #[cfg(feature = "native-tls")]
-            InnerTlsParameters::NativeTls(connector) => {
+            InnerTlsParameters::NativeTls(inner) => {
                #[cfg(not(feature = "tokio1-native-tls"))]
                panic!("built without the tokio1-native-tls feature");

@@ -329,16 +327,16 @@ impl AsyncNetworkStream {
                return {
                    use tokio1_native_tls_crate::TlsConnector;

-                    let connector = TlsConnector::from(connector);
+                    let connector = TlsConnector::from(inner.connector);
                    let stream = connector
-                        .connect(&domain, tcp_stream)
+                        .connect(&inner.server_name, tcp_stream)
                        .await
                        .map_err(error::connection)?;
                    Ok(InnerAsyncNetworkStream::Tokio1NativeTls(stream))
                };
            }
            #[cfg(feature = "rustls")]
-            InnerTlsParameters::RustlsTls(config) => {
+            InnerTlsParameters::Rustls(inner) => {
                #[cfg(not(feature = "tokio1-rustls"))]
                panic!("built without the tokio1-rustls feature");

@@ -346,28 +344,25 @@ impl AsyncNetworkStream {
                return {
                    use tokio1_rustls::TlsConnector;

-                    let domain = ServerName::try_from(domain.as_str())
-                        .map_err(|_| error::connection("domain isn't a valid DNS name"))?;
-
-                    let connector = TlsConnector::from(config);
+                    let connector = TlsConnector::from(inner.connector);
                    let stream = connector
-                        .connect(domain.to_owned(), tcp_stream)
+                        .connect(inner.server_name.inner(), tcp_stream)
                        .await
                        .map_err(error::connection)?;
-                    Ok(InnerAsyncNetworkStream::Tokio1RustlsTls(stream))
+                    Ok(InnerAsyncNetworkStream::Tokio1Rustls(stream))
                };
            }
            #[cfg(feature = "boring-tls")]
-            InnerTlsParameters::BoringTls(connector) => {
+            InnerTlsParameters::BoringTls(inner) => {
                #[cfg(not(feature = "tokio1-boring-tls"))]
                panic!("built without the tokio1-boring-tls feature");

                #[cfg(feature = "tokio1-boring-tls")]
                return {
-                    let mut config = connector.configure().map_err(error::connection)?;
-                    config.set_verify_hostname(tls_parameters.accept_invalid_hostnames);
+                    let mut config = inner.connector.configure().map_err(error::connection)?;
+                    config.set_verify_hostname(inner.extra_info.accept_invalid_hostnames);

-                    let stream = tokio1_boring::connect(config, &domain, tcp_stream)
+                    let stream = tokio1_boring::connect(config, &inner.server_name, tcp_stream)
                        .await
                        .map_err(error::connection)?;
                    Ok(InnerAsyncNetworkStream::Tokio1BoringTls(stream))
@@ -380,17 +375,15 @@ impl AsyncNetworkStream {
    #[cfg(feature = "async-std1-rustls")]
    async fn upgrade_asyncstd1_tls(
        tcp_stream: AsyncStd1TcpStream,
-        mut tls_parameters: TlsParameters,
+        tls_parameters: TlsParameters,
    ) -> Result<InnerAsyncNetworkStream, Error> {
-        let domain = mem::take(&mut tls_parameters.domain);
-
-        match tls_parameters.connector {
+        match tls_parameters.inner {
            #[cfg(feature = "native-tls")]
-            InnerTlsParameters::NativeTls(connector) => {
+            InnerTlsParameters::NativeTls(_) => {
                panic!("native-tls isn't supported with async-std yet. See https://github.com/lettre/lettre/pull/531#issuecomment-757893531");
            }
            #[cfg(feature = "rustls")]
-            InnerTlsParameters::RustlsTls(config) => {
+            InnerTlsParameters::Rustls(inner) => {
                #[cfg(not(feature = "async-std1-rustls"))]
                panic!("built without the async-std1-rustls feature");

@@ -398,19 +391,16 @@ impl AsyncNetworkStream {
                return {
                    use futures_rustls::TlsConnector;

-                    let domain = ServerName::try_from(domain.as_str())
-                        .map_err(|_| error::connection("domain isn't a valid DNS name"))?;
-
-                    let connector = TlsConnector::from(config);
+                    let connector = TlsConnector::from(inner.connector);
                    let stream = connector
-                        .connect(domain.to_owned(), tcp_stream)
+                        .connect(inner.server_name.inner(), tcp_stream)
                        .await
                        .map_err(error::connection)?;
-                    Ok(InnerAsyncNetworkStream::AsyncStd1RustlsTls(stream))
+                    Ok(InnerAsyncNetworkStream::AsyncStd1Rustls(stream))
                };
            }
            #[cfg(feature = "boring-tls")]
-            InnerTlsParameters::BoringTls(connector) => {
+            InnerTlsParameters::BoringTls(_inner) => {
                panic!("boring-tls isn't supported with async-std yet.");
            }
        }
@@ -423,18 +413,19 @@ impl AsyncNetworkStream {
            #[cfg(feature = "tokio1-native-tls")]
            InnerAsyncNetworkStream::Tokio1NativeTls(_) => true,
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(_) => true,
+            InnerAsyncNetworkStream::Tokio1Rustls(_) => true,
            #[cfg(feature = "tokio1-boring-tls")]
            InnerAsyncNetworkStream::Tokio1BoringTls(_) => true,
            #[cfg(feature = "async-std1")]
            InnerAsyncNetworkStream::AsyncStd1Tcp(_) => false,
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(_) => true,
+            InnerAsyncNetworkStream::AsyncStd1Rustls(_) => true,
            InnerAsyncNetworkStream::None => false,
        }
    }

    #[cfg(feature = "boring-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
    pub fn tls_verify_result(&self) -> Result<(), Error> {
        match &self.inner {
            #[cfg(feature = "tokio1")]
@@ -444,7 +435,7 @@ impl AsyncNetworkStream {
            #[cfg(feature = "tokio1-native-tls")]
            InnerAsyncNetworkStream::Tokio1NativeTls(_) => panic!("Unsupported"),
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(_) => panic!("Unsupported"),
+            InnerAsyncNetworkStream::Tokio1Rustls(_) => panic!("Unsupported"),
            #[cfg(feature = "tokio1-boring-tls")]
            InnerAsyncNetworkStream::Tokio1BoringTls(stream) => {
                stream.ssl().verify_result().map_err(error::tls)
@@ -454,10 +445,11 @@ impl AsyncNetworkStream {
                Err(error::client("Connection is not encrypted"))
            }
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(_) => panic!("Unsupported"),
+            InnerAsyncNetworkStream::AsyncStd1Rustls(_) => panic!("Unsupported"),
            InnerAsyncNetworkStream::None => panic!("InnerNetworkStream::None must never be built"),
        }
    }
+
    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
        match &self.inner {
            #[cfg(feature = "tokio1")]
@@ -467,7 +459,7 @@ impl AsyncNetworkStream {
            #[cfg(feature = "tokio1-native-tls")]
            InnerAsyncNetworkStream::Tokio1NativeTls(_) => panic!("Unsupported"),
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(stream) => Ok(stream
+            InnerAsyncNetworkStream::Tokio1Rustls(stream) => Ok(stream
                .get_ref()
                .1
                .peer_certificates()
@@ -488,7 +480,7 @@ impl AsyncNetworkStream {
                Err(error::client("Connection is not encrypted"))
            }
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(stream) => Ok(stream
+            InnerAsyncNetworkStream::AsyncStd1Rustls(stream) => Ok(stream
                .get_ref()
                .1
                .peer_certificates()
@@ -515,7 +507,7 @@ impl AsyncNetworkStream {
                .to_der()
                .map_err(error::tls)?),
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(stream) => Ok(stream
+            InnerAsyncNetworkStream::Tokio1Rustls(stream) => Ok(stream
                .get_ref()
                .1
                .peer_certificates()
@@ -535,7 +527,7 @@ impl AsyncNetworkStream {
                Err(error::client("Connection is not encrypted"))
            }
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(stream) => Ok(stream
+            InnerAsyncNetworkStream::AsyncStd1Rustls(stream) => Ok(stream
                .get_ref()
                .1
                .peer_certificates()
@@ -575,7 +567,7 @@ impl FuturesAsyncRead for AsyncNetworkStream {
                }
            }
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => {
+            InnerAsyncNetworkStream::Tokio1Rustls(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())),
@@ -595,7 +587,7 @@ impl FuturesAsyncRead for AsyncNetworkStream {
            #[cfg(feature = "async-std1")]
            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_read(cx, buf),
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_read(cx, buf),
+            InnerAsyncNetworkStream::AsyncStd1Rustls(s) => Pin::new(s).poll_read(cx, buf),
            InnerAsyncNetworkStream::None => {
                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
                Poll::Ready(Ok(0))
@@ -617,13 +609,13 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
            #[cfg(feature = "tokio1-native-tls")]
            InnerAsyncNetworkStream::Tokio1NativeTls(s) => Pin::new(s).poll_write(cx, buf),
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::Tokio1Rustls(s) => Pin::new(s).poll_write(cx, buf),
            #[cfg(feature = "tokio1-boring-tls")]
            InnerAsyncNetworkStream::Tokio1BoringTls(s) => Pin::new(s).poll_write(cx, buf),
            #[cfg(feature = "async-std1")]
            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_write(cx, buf),
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_write(cx, buf),
+            InnerAsyncNetworkStream::AsyncStd1Rustls(s) => Pin::new(s).poll_write(cx, buf),
            InnerAsyncNetworkStream::None => {
                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
                Poll::Ready(Ok(0))
@@ -638,13 +630,13 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
            #[cfg(feature = "tokio1-native-tls")]
            InnerAsyncNetworkStream::Tokio1NativeTls(s) => Pin::new(s).poll_flush(cx),
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::Tokio1Rustls(s) => Pin::new(s).poll_flush(cx),
            #[cfg(feature = "tokio1-boring-tls")]
            InnerAsyncNetworkStream::Tokio1BoringTls(s) => Pin::new(s).poll_flush(cx),
            #[cfg(feature = "async-std1")]
            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_flush(cx),
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_flush(cx),
+            InnerAsyncNetworkStream::AsyncStd1Rustls(s) => Pin::new(s).poll_flush(cx),
            InnerAsyncNetworkStream::None => {
                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
                Poll::Ready(Ok(()))
@@ -659,13 +651,13 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
            #[cfg(feature = "tokio1-native-tls")]
            InnerAsyncNetworkStream::Tokio1NativeTls(s) => Pin::new(s).poll_shutdown(cx),
            #[cfg(feature = "tokio1-rustls")]
-            InnerAsyncNetworkStream::Tokio1RustlsTls(s) => Pin::new(s).poll_shutdown(cx),
+            InnerAsyncNetworkStream::Tokio1Rustls(s) => Pin::new(s).poll_shutdown(cx),
            #[cfg(feature = "tokio1-boring-tls")]
            InnerAsyncNetworkStream::Tokio1BoringTls(s) => Pin::new(s).poll_shutdown(cx),
            #[cfg(feature = "async-std1")]
            InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_close(cx),
            #[cfg(feature = "async-std1-rustls")]
-            InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_close(cx),
+            InnerAsyncNetworkStream::AsyncStd1Rustls(s) => Pin::new(s).poll_close(cx),
            InnerAsyncNetworkStream::None => {
                debug_assert!(false, "InnerAsyncNetworkStream::None must never be built");
                Poll::Ready(Ok(()))
--- a/src/transport/smtp/client/connection.rs
+++ b/src/transport/smtp/client/connection.rs
@@ -300,6 +300,10 @@ impl SmtpConnection {

    /// The X509 certificate of the server (DER encoded)
    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+    )]
    pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
        self.stream.get_ref().peer_certificate()
    }
@@ -316,12 +320,14 @@ impl SmtpConnection {
    /// as the TLSA records match the leaf or issuer certificates.
    /// It cannot be called on non Boring TLS streams.
    #[cfg(feature = "boring-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
    pub fn tls_verify_result(&self) -> Result<(), Error> {
        self.stream.get_ref().tls_verify_result()
    }

    /// All the X509 certificates of the chain (DER encoded)
    #[cfg(any(feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "rustls", feature = "boring-tls"))))]
    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
        self.stream.get_ref().certificate_chain()
    }
--- a/src/transport/smtp/client/mod.rs
+++ b/src/transport/smtp/client/mod.rs
@@ -34,12 +34,14 @@ pub use self::async_net::AsyncNetworkStream;
 pub use self::async_net::AsyncTokioStream;
 use self::net::NetworkStream;
 #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
-pub(super) use self::tls::InnerTlsParameters;
+pub(super) use self::tls::current::InnerTlsParameters;
 #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
-pub use self::tls::TlsVersion;
+pub use self::tls::current::TlsVersion;
 pub use self::{
    connection::SmtpConnection,
-    tls::{Certificate, CertificateStore, Identity, Tls, TlsParameters, TlsParametersBuilder},
+    tls::current::{
+        Certificate, CertificateStore, Identity, Tls, TlsParameters, TlsParametersBuilder,
+    },
 };

 #[cfg(any(feature = "tokio1", feature = "async-std1"))]
@@ -58,7 +60,7 @@ struct ClientCodec {

 impl ClientCodec {
    /// Creates a new client codec
-    pub fn new() -> Self {
+    pub(crate) fn new() -> Self {
        Self {
            status: CodecStatus::StartOfNewLine,
        }
--- a/src/transport/smtp/client/net.rs
+++ b/src/transport/smtp/client/net.rs
@@ -12,7 +12,7 @@ use boring::ssl::SslStream;
 #[cfg(feature = "native-tls")]
 use native_tls::TlsStream;
 #[cfg(feature = "rustls")]
-use rustls::{pki_types::ServerName, ClientConnection, StreamOwned};
+use rustls::{ClientConnection, StreamOwned};
 use socket2::{Domain, Protocol, Type};

 #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
@@ -37,7 +37,7 @@ enum InnerNetworkStream {
    NativeTls(TlsStream<TcpStream>),
    /// Encrypted TCP stream
    #[cfg(feature = "rustls")]
-    RustlsTls(StreamOwned<ClientConnection, TcpStream>),
+    Rustls(StreamOwned<ClientConnection, TcpStream>),
    #[cfg(feature = "boring-tls")]
    BoringTls(SslStream<TcpStream>),
    /// Can't be built
@@ -60,7 +60,7 @@ impl NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(s) => s.get_ref().peer_addr(),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(s) => s.get_ref().peer_addr(),
+            InnerNetworkStream::Rustls(s) => s.get_ref().peer_addr(),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(s) => s.get_ref().peer_addr(),
            InnerNetworkStream::None => {
@@ -80,7 +80,7 @@ impl NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(s) => s.get_ref().shutdown(how),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(s) => s.get_ref().shutdown(how),
+            InnerNetworkStream::Rustls(s) => s.get_ref().shutdown(how),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(s) => s.get_ref().shutdown(how),
            InnerNetworkStream::None => {
@@ -172,30 +172,33 @@ impl NetworkStream {
        tcp_stream: TcpStream,
        tls_parameters: &TlsParameters,
    ) -> Result<InnerNetworkStream, Error> {
-        Ok(match &tls_parameters.connector {
+        Ok(match &tls_parameters.inner {
            #[cfg(feature = "native-tls")]
-            InnerTlsParameters::NativeTls(connector) => {
-                let stream = connector
-                    .connect(tls_parameters.domain(), tcp_stream)
+            InnerTlsParameters::NativeTls(inner) => {
+                let stream = inner
+                    .connector
+                    .connect(&inner.server_name, tcp_stream)
                    .map_err(error::connection)?;
                InnerNetworkStream::NativeTls(stream)
            }
            #[cfg(feature = "rustls")]
-            InnerTlsParameters::RustlsTls(connector) => {
-                let domain = ServerName::try_from(tls_parameters.domain())
-                    .map_err(|_| error::connection("domain isn't a valid DNS name"))?;
-                let connection = ClientConnection::new(Arc::clone(connector), domain.to_owned())
-                    .map_err(error::connection)?;
+            InnerTlsParameters::Rustls(inner) => {
+                let connection = ClientConnection::new(
+                    Arc::clone(&inner.connector),
+                    inner.server_name.inner_ref().clone(),
+                )
+                .map_err(error::connection)?;
                let stream = StreamOwned::new(connection, tcp_stream);
-                InnerNetworkStream::RustlsTls(stream)
+                InnerNetworkStream::Rustls(stream)
            }
            #[cfg(feature = "boring-tls")]
-            InnerTlsParameters::BoringTls(connector) => {
-                let stream = connector
+            InnerTlsParameters::BoringTls(inner) => {
+                let stream = inner
+                    .connector
                    .configure()
                    .map_err(error::connection)?
-                    .verify_hostname(tls_parameters.accept_invalid_hostnames)
-                    .connect(tls_parameters.domain(), tcp_stream)
+                    .verify_hostname(inner.extra_info.accept_invalid_hostnames)
+                    .connect(&inner.server_name, tcp_stream)
                    .map_err(error::connection)?;
                InnerNetworkStream::BoringTls(stream)
            }
@@ -208,7 +211,7 @@ impl NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(_) => true,
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(_) => true,
+            InnerNetworkStream::Rustls(_) => true,
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(_) => true,
            InnerNetworkStream::None => {
@@ -219,13 +222,14 @@ impl NetworkStream {
    }

    #[cfg(feature = "boring-tls")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
    pub fn tls_verify_result(&self) -> Result<(), Error> {
        match &self.inner {
            InnerNetworkStream::Tcp(_) => Err(error::client("Connection is not encrypted")),
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(_) => panic!("Unsupported"),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(_) => panic!("Unsupported"),
+            InnerNetworkStream::Rustls(_) => panic!("Unsupported"),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(stream) => {
                stream.ssl().verify_result().map_err(error::tls)
@@ -235,13 +239,14 @@ impl NetworkStream {
    }

    #[cfg(any(feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(docsrs, doc(cfg(any(feature = "rustls", feature = "boring-tls"))))]
    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
        match &self.inner {
            InnerNetworkStream::Tcp(_) => Err(error::client("Connection is not encrypted")),
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(_) => panic!("Unsupported"),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(stream) => Ok(stream
+            InnerNetworkStream::Rustls(stream) => Ok(stream
                .conn
                .peer_certificates()
                .unwrap()
@@ -261,6 +266,10 @@ impl NetworkStream {
    }

    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+    )]
    pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
        match &self.inner {
            InnerNetworkStream::Tcp(_) => Err(error::client("Connection is not encrypted")),
@@ -272,7 +281,7 @@ impl NetworkStream {
                .to_der()
                .map_err(error::tls)?),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(stream) => Ok(stream
+            InnerNetworkStream::Rustls(stream) => Ok(stream
                .conn
                .peer_certificates()
                .unwrap()
@@ -296,7 +305,7 @@ impl NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(stream) => stream.get_ref().set_read_timeout(duration),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(stream) => stream.get_ref().set_read_timeout(duration),
+            InnerNetworkStream::Rustls(stream) => stream.get_ref().set_read_timeout(duration),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(stream) => stream.get_ref().set_read_timeout(duration),
            InnerNetworkStream::None => {
@@ -314,7 +323,7 @@ impl NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(stream) => stream.get_ref().set_write_timeout(duration),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(stream) => stream.get_ref().set_write_timeout(duration),
+            InnerNetworkStream::Rustls(stream) => stream.get_ref().set_write_timeout(duration),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(stream) => stream.get_ref().set_write_timeout(duration),
            InnerNetworkStream::None => {
@@ -332,7 +341,7 @@ impl Read for NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(s) => s.read(buf),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(s) => s.read(buf),
+            InnerNetworkStream::Rustls(s) => s.read(buf),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(s) => s.read(buf),
            InnerNetworkStream::None => {
@@ -350,7 +359,7 @@ impl Write for NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(s) => s.write(buf),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(s) => s.write(buf),
+            InnerNetworkStream::Rustls(s) => s.write(buf),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(s) => s.write(buf),
            InnerNetworkStream::None => {
@@ -366,7 +375,7 @@ impl Write for NetworkStream {
            #[cfg(feature = "native-tls")]
            InnerNetworkStream::NativeTls(s) => s.flush(),
            #[cfg(feature = "rustls")]
-            InnerNetworkStream::RustlsTls(s) => s.flush(),
+            InnerNetworkStream::Rustls(s) => s.flush(),
            #[cfg(feature = "boring-tls")]
            InnerNetworkStream::BoringTls(s) => s.flush(),
            InnerNetworkStream::None => {
--- a/src/transport/smtp/client/tls/boring_tls.rs
+++ b/src/transport/smtp/client/tls/boring_tls.rs
@@ -0,0 +1,111 @@
+use std::fmt::{self, Debug};
+
+use boring::{
+    ssl::{SslConnector, SslMethod, SslVerifyMode, SslVersion},
+    x509::store::X509StoreBuilder,
+};
+
+use crate::transport::smtp::error::{self, Error};
+
+pub(super) fn build_connector(
+    builder: super::TlsParametersBuilder<super::BoringTls>,
+) -> Result<(Box<str>, SslConnector), Error> {
+    let mut tls_builder = SslConnector::builder(SslMethod::tls_client()).map_err(error::tls)?;
+
+    if builder.accept_invalid_certs {
+        tls_builder.set_verify(SslVerifyMode::NONE);
+    } else {
+        match builder.cert_store {
+            CertificateStore::System => {}
+            CertificateStore::None => {
+                // Replace the default store with an empty store.
+                tls_builder.set_cert_store(X509StoreBuilder::new().map_err(error::tls)?.build());
+            }
+        }
+
+        let cert_store = tls_builder.cert_store_mut();
+
+        for cert in builder.root_certs {
+            cert_store.add_cert(cert.0).map_err(error::tls)?;
+        }
+    }
+
+    if let Some(identity) = builder.identity {
+        tls_builder
+            .set_certificate(identity.chain.as_ref())
+            .map_err(error::tls)?;
+        tls_builder
+            .set_private_key(identity.key.as_ref())
+            .map_err(error::tls)?;
+    }
+
+    let min_tls_version = match builder.min_tls_version {
+        MinTlsVersion::Tlsv10 => SslVersion::TLS1,
+        MinTlsVersion::Tlsv11 => SslVersion::TLS1_1,
+        MinTlsVersion::Tlsv12 => SslVersion::TLS1_2,
+        MinTlsVersion::Tlsv13 => SslVersion::TLS1_3,
+    };
+
+    tls_builder
+        .set_min_proto_version(Some(min_tls_version))
+        .map_err(error::tls)?;
+    Ok((builder.server_name.into_boxed_str(), tls_builder.build()))
+}
+
+#[derive(Debug, Clone, Default)]
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+pub(super) enum CertificateStore {
+    #[default]
+    System,
+    None,
+}
+
+#[derive(Clone)]
+pub(super) struct Certificate(pub(super) boring::x509::X509);
+
+impl Certificate {
+    pub(super) fn from_pem(pem: &[u8]) -> Result<Self, Error> {
+        Ok(Self(boring::x509::X509::from_pem(pem).map_err(error::tls)?))
+    }
+
+    pub(super) fn from_der(der: &[u8]) -> Result<Self, Error> {
+        Ok(Self(boring::x509::X509::from_der(der).map_err(error::tls)?))
+    }
+}
+
+impl Debug for Certificate {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Certificate").finish_non_exhaustive()
+    }
+}
+
+#[derive(Clone)]
+pub(super) struct Identity {
+    pub(super) chain: boring::x509::X509,
+    pub(super) key: boring::pkey::PKey<boring::pkey::Private>,
+}
+
+impl Identity {
+    pub(super) fn from_pem(pem: &[u8], key: &[u8]) -> Result<Self, Error> {
+        let chain = boring::x509::X509::from_pem(pem).map_err(error::tls)?;
+        let key = boring::pkey::PKey::private_key_from_pem(key).map_err(error::tls)?;
+        Ok(Self { chain, key })
+    }
+}
+
+impl Debug for Identity {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Identity").finish_non_exhaustive()
+    }
+}
+
+#[derive(Debug, Copy, Clone, Default)]
+#[non_exhaustive]
+pub(super) enum MinTlsVersion {
+    Tlsv10,
+    Tlsv11,
+    #[default]
+    Tlsv12,
+    Tlsv13,
+}
--- a/src/transport/smtp/client/tls/current.rs
+++ b/src/transport/smtp/client/tls/current.rs
@@ -1,26 +1,9 @@
 use std::fmt::{self, Debug};
-#[cfg(feature = "rustls")]
-use std::sync::Arc;
-
-#[cfg(feature = "boring-tls")]
-use boring::{
-    pkey::PKey,
-    ssl::{SslConnector, SslVersion},
-    x509::store::X509StoreBuilder,
-};
-#[cfg(feature = "native-tls")]
-use native_tls::{Protocol, TlsConnector};
-#[cfg(feature = "rustls")]
-use rustls::{
-    client::danger::{HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier},
-    crypto::{verify_tls12_signature, verify_tls13_signature, CryptoProvider},
-    pki_types::{self, pem::PemObject, CertificateDer, PrivateKeyDer, ServerName, UnixTime},
-    server::ParsedCertificate,
-    ClientConfig, DigitallySignedStruct, Error as TlsError, RootCertStore, SignatureScheme,
-};

+use super::TlsBackend;
 #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
-use crate::transport::smtp::{error, Error};
+use crate::transport::smtp::error;
+use crate::transport::smtp::Error;

 /// TLS protocol versions.
 #[derive(Debug, Copy, Clone)]
@@ -65,6 +48,16 @@ pub enum TlsVersion {
 /// connecting to a local server.
 #[derive(Clone)]
 #[allow(missing_copy_implementations)]
+#[cfg_attr(
+    not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")),
+    deprecated(
+        note = "starting from lettre v0.12 `Tls` won't be available when none of the TLS backends are enabled"
+    )
+)]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+)]
 pub enum Tls {
    /// Insecure (plaintext) connection only.
    ///
@@ -138,14 +131,25 @@ impl Debug for Tls {
 /// Source for the base set of root certificates to trust.
 #[allow(missing_copy_implementations)]
 #[derive(Clone, Debug, Default)]
+#[cfg_attr(
+    not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")),
+    deprecated(
+        note = "starting from lettre v0.12 `CertificateStore` won't be available when none of the TLS backends are enabled"
+    )
+)]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+)]
 pub enum CertificateStore {
    /// Use the default for the TLS backend.
    ///
    /// For native-tls, this will use the system certificate store on Windows, the keychain on
    /// macOS, and OpenSSL directories on Linux (usually `/etc/ssl`).
    ///
-    /// For rustls, this will also use the system store if the `rustls-native-certs` feature is
-    /// enabled, or will fall back to `webpki-roots`.
+    /// For rustls, this will use the system certificate verifier if the `rustls-platform-verifier`
+    /// feature is enabled. If the `rustls-native-certs` feature is enabled, system certificate
+    /// store will be used. Otherwise, it will fall back to `webpki-roots`.
    ///
    /// The boring-tls backend uses the same logic as OpenSSL on all platforms.
    #[default]
@@ -161,16 +165,32 @@ pub enum CertificateStore {

 /// Parameters to use for secure clients
 #[derive(Clone)]
+#[cfg_attr(
+    not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")),
+    deprecated(
+        note = "starting from lettre v0.12 `TlsParameters` won't be available when none of the TLS backends are enabled"
+    )
+)]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+)]
 pub struct TlsParameters {
-    pub(crate) connector: InnerTlsParameters,
-    /// The domain name which is expected in the TLS certificate from the server
-    pub(super) domain: String,
-    #[cfg(feature = "boring-tls")]
-    pub(super) accept_invalid_hostnames: bool,
+    pub(in crate::transport::smtp) inner: InnerTlsParameters,
 }

 /// Builder for `TlsParameters`
 #[derive(Debug, Clone)]
+#[cfg_attr(
+    not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")),
+    deprecated(
+        note = "starting from lettre v0.12 `TlsParametersBuilder` won't be available when none of the TLS backends are enabled"
+    )
+)]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+)]
 pub struct TlsParametersBuilder {
    domain: String,
    cert_store: CertificateStore,
@@ -221,6 +241,8 @@ impl TlsParametersBuilder {

    /// Controls whether certificates with an invalid hostname are accepted
    ///
+    /// This option is silently disabled when using `rustls-platform-verifier`.
+    ///
    /// Defaults to `false`.
    ///
    /// # Warning
@@ -244,6 +266,10 @@ impl TlsParametersBuilder {
    ///
    /// Defaults to [`Tlsv12`][TlsVersion::Tlsv12].
    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+    )]
    pub fn set_min_tls_version(mut self, min_tls_version: TlsVersion) -> Self {
        self.min_tls_version = min_tls_version;
        self
@@ -290,30 +316,20 @@ impl TlsParametersBuilder {
    #[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();
-
-        match self.cert_store {
-            CertificateStore::Default => {}
-            CertificateStore::None => {
-                tls_builder.disable_built_in_roots(true);
-            }
+        let cert_store = match self.cert_store {
+            CertificateStore::Default => super::native_tls::CertificateStore::System,
+            CertificateStore::None => super::native_tls::CertificateStore::None,
            #[allow(unreachable_patterns)]
            other => {
                return Err(error::tls(format!(
                    "{other:?} is not supported in native tls"
                )))
            }
-        }
-        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);
-
+        };
        let min_tls_version = match self.min_tls_version {
-            TlsVersion::Tlsv10 => Protocol::Tlsv10,
-            TlsVersion::Tlsv11 => Protocol::Tlsv11,
-            TlsVersion::Tlsv12 => Protocol::Tlsv12,
+            TlsVersion::Tlsv10 => super::native_tls::MinTlsVersion::Tlsv10,
+            TlsVersion::Tlsv11 => super::native_tls::MinTlsVersion::Tlsv11,
+            TlsVersion::Tlsv12 => super::native_tls::MinTlsVersion::Tlsv12,
            TlsVersion::Tlsv13 => {
                return Err(error::tls(
                    "min tls version Tlsv13 not supported in native tls",
@@ -321,182 +337,114 @@ impl TlsParametersBuilder {
            }
        };

-        tls_builder.min_protocol_version(Some(min_tls_version));
+        let mut builder = super::TlsParametersBuilder::<super::NativeTls>::new(self.domain)
+            .certificate_store(cert_store)
+            .dangerous_accept_invalid_certs(self.accept_invalid_certs)
+            .dangerous_accept_invalid_hostnames(self.accept_invalid_hostnames)
+            .min_tls_version(min_tls_version);
+        for cert in self.root_certs {
+            builder = builder.add_root_certificate(cert.native_tls);
+        }
        if let Some(identity) = self.identity {
-            tls_builder.identity(identity.native_tls);
+            builder = builder.identify_with(identity.native_tls);
        }

-        let connector = tls_builder.build().map_err(error::tls)?;
-        Ok(TlsParameters {
-            connector: InnerTlsParameters::NativeTls(connector),
-            domain: self.domain,
-            #[cfg(feature = "boring-tls")]
-            accept_invalid_hostnames: self.accept_invalid_hostnames,
-        })
+        builder
+            .build()
+            .map(super::NativeTls::__build_current_tls_parameters)
    }

    /// Creates a new `TlsParameters` using boring-tls with the provided configuration
+    ///
+    /// Warning: this uses the certificate store passed via `certificate_store`
+    /// instead of the one configured in [`TlsParametersBuilder::certificate_store`].
    #[cfg(feature = "boring-tls")]
    #[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
    pub fn build_boring(self) -> Result<TlsParameters, Error> {
-        use boring::ssl::{SslMethod, SslVerifyMode};
-
-        let mut tls_builder = SslConnector::builder(SslMethod::tls_client()).map_err(error::tls)?;
-
-        if self.accept_invalid_certs {
-            tls_builder.set_verify(SslVerifyMode::NONE);
-        } else {
-            match self.cert_store {
-                CertificateStore::Default => {}
-                CertificateStore::None => {
-                    // Replace the default store with an empty store.
-                    tls_builder
-                        .set_cert_store(X509StoreBuilder::new().map_err(error::tls)?.build());
-                }
-                #[allow(unreachable_patterns)]
-                other => {
-                    return Err(error::tls(format!(
-                        "{other:?} is not supported in boring tls"
-                    )))
-                }
+        let cert_store = match self.cert_store {
+            CertificateStore::Default => super::boring_tls::CertificateStore::System,
+            CertificateStore::None => super::boring_tls::CertificateStore::None,
+            #[allow(unreachable_patterns)]
+            other => {
+                return Err(error::tls(format!(
+                    "{other:?} is not supported in native tls"
+                )))
            }
-
-            let cert_store = tls_builder.cert_store_mut();
-
-            for cert in self.root_certs {
-                cert_store.add_cert(cert.boring_tls).map_err(error::tls)?;
-            }
-        }
-
-        if let Some(identity) = self.identity {
-            tls_builder
-                .set_certificate(identity.boring_tls.0.as_ref())
-                .map_err(error::tls)?;
-            tls_builder
-                .set_private_key(identity.boring_tls.1.as_ref())
-                .map_err(error::tls)?;
-        }
-
+        };
        let min_tls_version = match self.min_tls_version {
-            TlsVersion::Tlsv10 => SslVersion::TLS1,
-            TlsVersion::Tlsv11 => SslVersion::TLS1_1,
-            TlsVersion::Tlsv12 => SslVersion::TLS1_2,
-            TlsVersion::Tlsv13 => SslVersion::TLS1_3,
+            TlsVersion::Tlsv10 => super::boring_tls::MinTlsVersion::Tlsv10,
+            TlsVersion::Tlsv11 => super::boring_tls::MinTlsVersion::Tlsv11,
+            TlsVersion::Tlsv12 => super::boring_tls::MinTlsVersion::Tlsv12,
+            TlsVersion::Tlsv13 => super::boring_tls::MinTlsVersion::Tlsv13,
        };

-        tls_builder
-            .set_min_proto_version(Some(min_tls_version))
-            .map_err(error::tls)?;
-        let connector = tls_builder.build();
-        Ok(TlsParameters {
-            connector: InnerTlsParameters::BoringTls(connector),
-            domain: self.domain,
-            accept_invalid_hostnames: self.accept_invalid_hostnames,
-        })
+        let mut builder = super::TlsParametersBuilder::<super::BoringTls>::new(self.domain)
+            .certificate_store(cert_store)
+            .dangerous_accept_invalid_certs(self.accept_invalid_certs)
+            .dangerous_accept_invalid_hostnames(self.accept_invalid_hostnames)
+            .min_tls_version(min_tls_version);
+        for cert in self.root_certs {
+            builder = builder.add_root_certificate(cert.boring_tls);
+        }
+        if let Some(identity) = self.identity {
+            builder = builder.identify_with(identity.boring_tls);
+        }
+
+        builder
+            .build()
+            .map(super::BoringTls::__build_current_tls_parameters)
    }

    /// Creates a new `TlsParameters` using rustls with the provided configuration
    #[cfg(feature = "rustls")]
    #[cfg_attr(docsrs, doc(cfg(feature = "rustls")))]
    pub fn build_rustls(self) -> Result<TlsParameters, Error> {
-        let just_version3 = &[&rustls::version::TLS13];
-        let supported_versions = match self.min_tls_version {
+        let cert_store = match self.cert_store {
+            CertificateStore::Default => super::rustls::CertificateStore::default(),
+            #[cfg(feature = "webpki-roots")]
+            CertificateStore::WebpkiRoots => super::rustls::CertificateStore::WebpkiRoots,
+            CertificateStore::None => super::rustls::CertificateStore::None,
+        };
+        let min_tls_version = match self.min_tls_version {
            TlsVersion::Tlsv10 => {
                return Err(error::tls("min tls version Tlsv10 not supported in rustls"))
            }
            TlsVersion::Tlsv11 => {
                return Err(error::tls("min tls version Tlsv11 not supported in rustls"))
            }
-            TlsVersion::Tlsv12 => rustls::ALL_VERSIONS,
-            TlsVersion::Tlsv13 => just_version3,
+            TlsVersion::Tlsv12 => super::rustls::MinTlsVersion::Tlsv12,
+            TlsVersion::Tlsv13 => super::rustls::MinTlsVersion::Tlsv13,
        };

-        let crypto_provider = crate::rustls_crypto::crypto_provider();
-        let tls = ClientConfig::builder_with_provider(Arc::clone(&crypto_provider))
-            .with_protocol_versions(supported_versions)
-            .map_err(error::tls)?;
-
-        // Build TLS config
-        let mut root_cert_store = RootCertStore::empty();
-
-        #[cfg(feature = "rustls-native-certs")]
-        fn load_native_roots(store: &mut RootCertStore) {
-            let rustls_native_certs::CertificateResult { certs, errors, .. } =
-                rustls_native_certs::load_native_certs();
-            let errors_len = errors.len();
-
-            let (added, ignored) = store.add_parsable_certificates(certs);
-            #[cfg(feature = "tracing")]
-            tracing::debug!(
-                "loaded platform certs with {errors_len} failing to load, {added} valid and {ignored} ignored (invalid) certs"
-            );
-            #[cfg(not(feature = "tracing"))]
-            let _ = (errors_len, added, ignored);
-        }
-
-        #[cfg(all(feature = "rustls", feature = "webpki-roots"))]
-        fn load_webpki_roots(store: &mut RootCertStore) {
-            store.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
-        }
-
-        match self.cert_store {
-            CertificateStore::Default => {
-                #[cfg(feature = "rustls-native-certs")]
-                load_native_roots(&mut root_cert_store);
-                #[cfg(all(not(feature = "rustls-native-certs"), feature = "webpki-roots"))]
-                load_webpki_roots(&mut root_cert_store);
-            }
-            #[cfg(all(feature = "rustls", feature = "webpki-roots"))]
-            CertificateStore::WebpkiRoots => {
-                load_webpki_roots(&mut root_cert_store);
-            }
-            CertificateStore::None => {}
-        }
+        let mut builder = super::TlsParametersBuilder::<super::Rustls>::new(self.domain)
+            .certificate_store(cert_store)
+            .dangerous_accept_invalid_certs(self.accept_invalid_certs)
+            .dangerous_accept_invalid_hostnames(self.accept_invalid_hostnames)
+            .min_tls_version(min_tls_version);
        for cert in self.root_certs {
-            for rustls_cert in cert.rustls {
-                root_cert_store.add(rustls_cert).map_err(error::tls)?;
+            for cert in cert.rustls {
+                builder = builder.add_root_certificate(cert);
            }
        }
+        if let Some(identity) = self.identity {
+            builder = builder.identify_with(identity.rustls_tls);
+        }

-        let tls = if self.accept_invalid_certs || self.accept_invalid_hostnames {
-            let verifier = InvalidCertsVerifier {
-                ignore_invalid_hostnames: self.accept_invalid_hostnames,
-                ignore_invalid_certs: self.accept_invalid_certs,
-                roots: root_cert_store,
-                crypto_provider,
-            };
-            tls.dangerous()
-                .with_custom_certificate_verifier(Arc::new(verifier))
-        } else {
-            tls.with_root_certificates(root_cert_store)
-        };
-
-        let tls = if let Some(identity) = self.identity {
-            let (client_certificates, private_key) = identity.rustls_tls;
-            tls.with_client_auth_cert(client_certificates, private_key)
-                .map_err(error::tls)?
-        } else {
-            tls.with_no_client_auth()
-        };
-
-        Ok(TlsParameters {
-            connector: InnerTlsParameters::RustlsTls(Arc::new(tls)),
-            domain: self.domain,
-            #[cfg(feature = "boring-tls")]
-            accept_invalid_hostnames: self.accept_invalid_hostnames,
-        })
+        builder
+            .build()
+            .map(super::Rustls::__build_current_tls_parameters)
    }
 }

 #[derive(Clone)]
 #[allow(clippy::enum_variant_names)]
-pub enum InnerTlsParameters {
+pub(in crate::transport::smtp) enum InnerTlsParameters {
    #[cfg(feature = "native-tls")]
-    NativeTls(TlsConnector),
+    NativeTls(super::TlsParameters<super::NativeTls>),
    #[cfg(feature = "rustls")]
-    RustlsTls(Arc<ClientConfig>),
+    Rustls(super::TlsParameters<super::Rustls>),
    #[cfg(feature = "boring-tls")]
-    BoringTls(SslConnector),
+    BoringTls(super::TlsParameters<super::BoringTls>),
 }

 impl TlsParameters {
@@ -508,7 +456,7 @@ impl TlsParameters {
        doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
    )]
    pub fn new(domain: String) -> Result<Self, Error> {
-        TlsParametersBuilder::new(domain).build()
+        Self::new_with::<super::DefaultTlsBackend>(domain)
    }

    /// Creates a new `TlsParameters` builder
@@ -520,82 +468,86 @@ impl TlsParameters {
    #[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()
+        Self::new_with::<super::NativeTls>(domain)
    }

    /// Creates a new `TlsParameters` using rustls
    #[cfg(feature = "rustls")]
    #[cfg_attr(docsrs, doc(cfg(feature = "rustls")))]
    pub fn new_rustls(domain: String) -> Result<Self, Error> {
-        TlsParametersBuilder::new(domain).build_rustls()
+        Self::new_with::<super::Rustls>(domain)
    }

    /// Creates a new `TlsParameters` using boring
    #[cfg(feature = "boring-tls")]
    #[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
    pub fn new_boring(domain: String) -> Result<Self, Error> {
-        TlsParametersBuilder::new(domain).build_boring()
+        Self::new_with::<super::BoringTls>(domain)
+    }
+
+    fn new_with<B: TlsBackend>(domain: String) -> Result<Self, Error> {
+        super::TlsParametersBuilder::<B>::new(domain)
+            .build()
+            .map(B::__build_current_tls_parameters)
    }

    pub fn domain(&self) -> &str {
-        &self.domain
+        match self.inner {
+            #[cfg(feature = "native-tls")]
+            InnerTlsParameters::NativeTls(ref inner) => &inner.server_name,
+            #[cfg(feature = "rustls")]
+            InnerTlsParameters::Rustls(ref inner) => inner.server_name.as_ref(),
+            #[cfg(feature = "boring-tls")]
+            InnerTlsParameters::BoringTls(ref inner) => &inner.server_name,
+        }
    }
 }

 /// A certificate that can be used with [`TlsParametersBuilder::add_root_certificate`]
 #[derive(Clone)]
 #[allow(missing_copy_implementations)]
+#[cfg_attr(
+    not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")),
+    deprecated(
+        note = "starting from lettre v0.12 `Certificate` won't be available when none of the TLS backends are enabled"
+    )
+)]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+)]
 pub struct Certificate {
    #[cfg(feature = "native-tls")]
-    native_tls: native_tls::Certificate,
+    native_tls: super::native_tls::Certificate,
    #[cfg(feature = "rustls")]
-    rustls: Vec<CertificateDer<'static>>,
+    rustls: Vec<super::rustls::Certificate>,
    #[cfg(feature = "boring-tls")]
-    boring_tls: boring::x509::X509,
+    boring_tls: super::boring_tls::Certificate,
 }

 #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
 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::tls)?;
-
-        #[cfg(feature = "boring-tls")]
-        let boring_tls_cert = boring::x509::X509::from_der(&der).map_err(error::tls)?;
-
        Ok(Self {
            #[cfg(feature = "native-tls")]
-            native_tls: native_tls_cert,
-            #[cfg(feature = "rustls")]
-            rustls: vec![der.into()],
+            native_tls: super::native_tls::Certificate::from_der(&der)?,
            #[cfg(feature = "boring-tls")]
-            boring_tls: boring_tls_cert,
+            boring_tls: super::boring_tls::Certificate::from_der(&der)?,
+            #[cfg(feature = "rustls")]
+            rustls: vec![super::rustls::Certificate::from_der(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::tls)?;
-
-        #[cfg(feature = "boring-tls")]
-        let boring_tls_cert = boring::x509::X509::from_pem(pem).map_err(error::tls)?;
-
-        #[cfg(feature = "rustls")]
-        let rustls_cert = {
-            CertificateDer::pem_slice_iter(pem)
-                .collect::<Result<Vec<_>, pki_types::pem::Error>>()
-                .map_err(|_| error::tls("invalid certificates"))?
-        };
-
        Ok(Self {
            #[cfg(feature = "native-tls")]
-            native_tls: native_tls_cert,
+            native_tls: super::native_tls::Certificate::from_pem(pem)?,
            #[cfg(feature = "rustls")]
-            rustls: rustls_cert,
+            rustls: super::rustls::Certificate::from_pem_bundle(pem)?,
            #[cfg(feature = "boring-tls")]
-            boring_tls: boring_tls_cert,
+            boring_tls: super::boring_tls::Certificate::from_pem(pem)?,
        })
    }
 }
@@ -607,14 +559,25 @@ impl Debug for Certificate {
 }

 /// An identity that can be used with [`TlsParametersBuilder::identify_with`]
+#[derive(Clone)]
 #[allow(missing_copy_implementations)]
+#[cfg_attr(
+    not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")),
+    deprecated(
+        note = "starting from lettre v0.12 `Identity` won't be available when none of the TLS backends are enabled"
+    )
+)]
+#[cfg_attr(
+    docsrs,
+    doc(cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))
+)]
 pub struct Identity {
    #[cfg(feature = "native-tls")]
-    native_tls: native_tls::Identity,
+    native_tls: super::native_tls::Identity,
    #[cfg(feature = "rustls")]
-    rustls_tls: (Vec<CertificateDer<'static>>, PrivateKeyDer<'static>),
+    rustls_tls: super::rustls::Identity,
    #[cfg(feature = "boring-tls")]
-    boring_tls: (boring::x509::X509, PKey<boring::pkey::Private>),
+    boring_tls: super::boring_tls::Identity,
 }

 impl Debug for Identity {
@@ -623,132 +586,16 @@ impl Debug for Identity {
    }
 }

-impl Clone for Identity {
-    fn clone(&self) -> Self {
-        Identity {
-            #[cfg(feature = "native-tls")]
-            native_tls: self.native_tls.clone(),
-            #[cfg(feature = "rustls")]
-            rustls_tls: (self.rustls_tls.0.clone(), self.rustls_tls.1.clone_key()),
-            #[cfg(feature = "boring-tls")]
-            boring_tls: (self.boring_tls.0.clone(), self.boring_tls.1.clone()),
-        }
-    }
-}
-
 #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
 impl Identity {
    pub fn from_pem(pem: &[u8], key: &[u8]) -> Result<Self, Error> {
        Ok(Self {
            #[cfg(feature = "native-tls")]
-            native_tls: Identity::from_pem_native_tls(pem, key)?,
+            native_tls: super::native_tls::Identity::from_pem(pem, key)?,
            #[cfg(feature = "rustls")]
-            rustls_tls: Identity::from_pem_rustls_tls(pem, key)?,
+            rustls_tls: super::rustls::Identity::from_pem(pem, key)?,
            #[cfg(feature = "boring-tls")]
-            boring_tls: Identity::from_pem_boring_tls(pem, key)?,
+            boring_tls: super::boring_tls::Identity::from_pem(pem, key)?,
        })
    }
-
-    #[cfg(feature = "native-tls")]
-    fn from_pem_native_tls(pem: &[u8], key: &[u8]) -> Result<native_tls::Identity, Error> {
-        native_tls::Identity::from_pkcs8(pem, key).map_err(error::tls)
-    }
-
-    #[cfg(feature = "rustls")]
-    fn from_pem_rustls_tls(
-        pem: &[u8],
-        key: &[u8],
-    ) -> Result<(Vec<CertificateDer<'static>>, PrivateKeyDer<'static>), Error> {
-        let key = match PrivateKeyDer::from_pem_slice(key) {
-            Ok(key) => key,
-            Err(pki_types::pem::Error::NoItemsFound) => {
-                return Err(error::tls("no private key found"))
-            }
-            Err(err) => return Err(error::tls(err)),
-        };
-
-        Ok((vec![pem.to_owned().into()], key))
-    }
-
-    #[cfg(feature = "boring-tls")]
-    fn from_pem_boring_tls(
-        pem: &[u8],
-        key: &[u8],
-    ) -> Result<(boring::x509::X509, PKey<boring::pkey::Private>), Error> {
-        let cert = boring::x509::X509::from_pem(pem).map_err(error::tls)?;
-        let key = boring::pkey::PKey::private_key_from_pem(key).map_err(error::tls)?;
-        Ok((cert, key))
-    }
-}
-
-#[cfg(feature = "rustls")]
-#[derive(Debug)]
-struct InvalidCertsVerifier {
-    ignore_invalid_hostnames: bool,
-    ignore_invalid_certs: bool,
-    roots: RootCertStore,
-    crypto_provider: Arc<CryptoProvider>,
-}
-
-#[cfg(feature = "rustls")]
-impl ServerCertVerifier for InvalidCertsVerifier {
-    fn verify_server_cert(
-        &self,
-        end_entity: &CertificateDer<'_>,
-        intermediates: &[CertificateDer<'_>],
-        server_name: &ServerName<'_>,
-        _ocsp_response: &[u8],
-        now: UnixTime,
-    ) -> Result<ServerCertVerified, TlsError> {
-        let cert = ParsedCertificate::try_from(end_entity)?;
-
-        if !self.ignore_invalid_certs {
-            rustls::client::verify_server_cert_signed_by_trust_anchor(
-                &cert,
-                &self.roots,
-                intermediates,
-                now,
-                self.crypto_provider.signature_verification_algorithms.all,
-            )?;
-        }
-
-        if !self.ignore_invalid_hostnames {
-            rustls::client::verify_server_name(&cert, server_name)?;
-        }
-        Ok(ServerCertVerified::assertion())
-    }
-
-    fn verify_tls12_signature(
-        &self,
-        message: &[u8],
-        cert: &CertificateDer<'_>,
-        dss: &DigitallySignedStruct,
-    ) -> Result<HandshakeSignatureValid, TlsError> {
-        verify_tls12_signature(
-            message,
-            cert,
-            dss,
-            &self.crypto_provider.signature_verification_algorithms,
-        )
-    }
-
-    fn verify_tls13_signature(
-        &self,
-        message: &[u8],
-        cert: &CertificateDer<'_>,
-        dss: &DigitallySignedStruct,
-    ) -> Result<HandshakeSignatureValid, TlsError> {
-        verify_tls13_signature(
-            message,
-            cert,
-            dss,
-            &self.crypto_provider.signature_verification_algorithms,
-        )
-    }
-
-    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
-        self.crypto_provider
-            .signature_verification_algorithms
-            .supported_schemes()
-    }
 }
--- a/src/transport/smtp/client/tls/mod.rs
+++ b/src/transport/smtp/client/tls/mod.rs
@@ -0,0 +1,253 @@
+use crate::transport::smtp::Error;
+
+#[cfg(feature = "boring-tls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
+pub(super) mod boring_tls;
+pub(super) mod current;
+#[cfg(feature = "native-tls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+pub(super) mod native_tls;
+#[cfg(feature = "rustls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "rustls")))]
+pub(super) mod rustls;
+
+#[derive(Debug)]
+#[allow(private_bounds)]
+pub(in crate::transport::smtp) struct TlsParameters<B: TlsBackend> {
+    pub(in crate::transport::smtp) server_name: B::ServerName,
+    pub(in crate::transport::smtp) connector: B::Connector,
+    pub(in crate::transport::smtp) extra_info: B::ExtraInfo,
+}
+
+impl<B: TlsBackend> Clone for TlsParameters<B> {
+    fn clone(&self) -> Self {
+        Self {
+            server_name: self.server_name.clone(),
+            connector: self.connector.clone(),
+            extra_info: self.extra_info.clone(),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct TlsParametersBuilder<B: TlsBackend> {
+    server_name: String,
+    cert_store: B::CertificateStore,
+    root_certs: Vec<B::Certificate>,
+    identity: Option<B::Identity>,
+    accept_invalid_certs: bool,
+    accept_invalid_hostnames: bool,
+    min_tls_version: B::MinTlsVersion,
+}
+
+impl<B: TlsBackend> TlsParametersBuilder<B> {
+    fn new(server_name: String) -> Self {
+        Self {
+            server_name,
+            cert_store: Default::default(),
+            root_certs: Vec::new(),
+            identity: None,
+            accept_invalid_certs: false,
+            accept_invalid_hostnames: false,
+            min_tls_version: Default::default(),
+        }
+    }
+
+    fn certificate_store(mut self, cert_store: B::CertificateStore) -> Self {
+        self.cert_store = cert_store;
+        self
+    }
+
+    fn add_root_certificate(mut self, cert: B::Certificate) -> Self {
+        self.root_certs.push(cert);
+        self
+    }
+
+    fn identify_with(mut self, identity: B::Identity) -> Self {
+        self.identity = Some(identity);
+        self
+    }
+
+    fn min_tls_version(mut self, min_tls_version: B::MinTlsVersion) -> Self {
+        self.min_tls_version = min_tls_version;
+        self
+    }
+
+    fn dangerous_accept_invalid_certs(mut self, accept_invalid_certs: bool) -> Self {
+        self.accept_invalid_certs = accept_invalid_certs;
+        self
+    }
+
+    fn dangerous_accept_invalid_hostnames(mut self, accept_invalid_hostnames: bool) -> Self {
+        self.accept_invalid_hostnames = accept_invalid_hostnames;
+        self
+    }
+
+    fn build(self) -> Result<TlsParameters<B>, Error> {
+        B::__build_connector(self)
+    }
+}
+
+#[allow(private_bounds)]
+trait TlsBackend: private::SealedTlsBackend {
+    type CertificateStore: Default;
+    type Certificate;
+    type Identity;
+    type MinTlsVersion: Default;
+
+    #[doc(hidden)]
+    fn __build_connector(builder: TlsParametersBuilder<Self>)
+        -> Result<TlsParameters<Self>, Error>;
+
+    #[doc(hidden)]
+    fn __build_current_tls_parameters(inner: TlsParameters<Self>) -> self::current::TlsParameters;
+}
+
+#[cfg(feature = "native-tls")]
+type DefaultTlsBackend = NativeTls;
+
+#[cfg(all(feature = "rustls", not(feature = "native-tls")))]
+type DefaultTlsBackend = Rustls;
+
+#[cfg(all(
+    feature = "boring-tls",
+    not(feature = "native-tls"),
+    not(feature = "rustls")
+))]
+type DefaultTlsBackend = BoringTls;
+
+#[cfg(feature = "native-tls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+#[derive(Debug)]
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+pub(in crate::transport::smtp) struct NativeTls;
+
+#[cfg(feature = "native-tls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "native-tls")))]
+impl TlsBackend for NativeTls {
+    type CertificateStore = self::native_tls::CertificateStore;
+    type Certificate = self::native_tls::Certificate;
+    type Identity = self::native_tls::Identity;
+    type MinTlsVersion = self::native_tls::MinTlsVersion;
+
+    fn __build_connector(
+        builder: TlsParametersBuilder<Self>,
+    ) -> Result<TlsParameters<Self>, Error> {
+        self::native_tls::build_connector(builder).map(|(server_name, connector)| TlsParameters {
+            server_name,
+            connector,
+            extra_info: (),
+        })
+    }
+
+    fn __build_current_tls_parameters(inner: TlsParameters<Self>) -> self::current::TlsParameters {
+        self::current::TlsParameters {
+            inner: self::current::InnerTlsParameters::NativeTls(inner),
+        }
+    }
+}
+
+#[cfg(feature = "rustls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "rustls")))]
+#[derive(Debug)]
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+pub(in crate::transport::smtp) struct Rustls;
+
+#[cfg(feature = "rustls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "rustls")))]
+impl TlsBackend for Rustls {
+    type CertificateStore = self::rustls::CertificateStore;
+    type Certificate = self::rustls::Certificate;
+    type Identity = self::rustls::Identity;
+    type MinTlsVersion = self::rustls::MinTlsVersion;
+
+    fn __build_connector(
+        builder: TlsParametersBuilder<Self>,
+    ) -> Result<TlsParameters<Self>, Error> {
+        self::rustls::build_connector(builder).map(|(server_name, connector)| TlsParameters {
+            server_name,
+            connector,
+            extra_info: (),
+        })
+    }
+
+    fn __build_current_tls_parameters(inner: TlsParameters<Self>) -> self::current::TlsParameters {
+        self::current::TlsParameters {
+            inner: self::current::InnerTlsParameters::Rustls(inner),
+        }
+    }
+}
+
+#[cfg(feature = "boring-tls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
+#[derive(Debug)]
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+pub(in crate::transport::smtp) struct BoringTls;
+
+#[cfg(feature = "boring-tls")]
+#[cfg_attr(docsrs, doc(cfg(feature = "boring-tls")))]
+impl TlsBackend for BoringTls {
+    type CertificateStore = self::boring_tls::CertificateStore;
+    type Certificate = self::boring_tls::Certificate;
+    type Identity = self::boring_tls::Identity;
+    type MinTlsVersion = self::boring_tls::MinTlsVersion;
+
+    fn __build_connector(
+        builder: TlsParametersBuilder<Self>,
+    ) -> Result<TlsParameters<Self>, Error> {
+        let accept_invalid_hostnames = builder.accept_invalid_hostnames;
+        self::boring_tls::build_connector(builder).map(|(server_name, connector)| TlsParameters {
+            server_name,
+            connector,
+            extra_info: BoringTlsExtraInfo {
+                accept_invalid_hostnames,
+            },
+        })
+    }
+
+    fn __build_current_tls_parameters(inner: TlsParameters<Self>) -> self::current::TlsParameters {
+        self::current::TlsParameters {
+            inner: self::current::InnerTlsParameters::BoringTls(inner),
+        }
+    }
+}
+
+#[cfg(feature = "boring-tls")]
+#[derive(Debug, Clone)]
+pub(in crate::transport::smtp) struct BoringTlsExtraInfo {
+    pub(super) accept_invalid_hostnames: bool,
+}
+
+mod private {
+    pub(in crate::transport::smtp) trait SealedTlsBackend:
+        Sized
+    {
+        type ServerName: Clone + AsRef<str>;
+        type Connector: Clone;
+        type ExtraInfo: Clone;
+    }
+
+    #[cfg(feature = "native-tls")]
+    impl SealedTlsBackend for super::NativeTls {
+        type ServerName = Box<str>;
+        type Connector = native_tls::TlsConnector;
+        type ExtraInfo = ();
+    }
+
+    #[cfg(feature = "rustls")]
+    impl SealedTlsBackend for super::Rustls {
+        type ServerName = super::rustls::ServerName;
+        type Connector = std::sync::Arc<rustls::client::ClientConfig>;
+        type ExtraInfo = ();
+    }
+
+    #[cfg(feature = "boring-tls")]
+    impl SealedTlsBackend for super::BoringTls {
+        type ServerName = Box<str>;
+        type Connector = boring::ssl::SslConnector;
+        type ExtraInfo = super::BoringTlsExtraInfo;
+    }
+}
--- a/src/transport/smtp/client/tls/native_tls.rs
+++ b/src/transport/smtp/client/tls/native_tls.rs
@@ -0,0 +1,95 @@
+use std::fmt::{self, Debug};
+
+use native_tls::TlsConnector;
+
+use crate::transport::smtp::error::{self, Error};
+
+pub(super) fn build_connector(
+    builder: super::TlsParametersBuilder<super::NativeTls>,
+) -> Result<(Box<str>, TlsConnector), Error> {
+    let mut tls_builder = TlsConnector::builder();
+
+    match builder.cert_store {
+        CertificateStore::System => {}
+        CertificateStore::None => {
+            tls_builder.disable_built_in_roots(true);
+        }
+    }
+    for cert in builder.root_certs {
+        tls_builder.add_root_certificate(cert.0);
+    }
+    tls_builder.danger_accept_invalid_hostnames(builder.accept_invalid_hostnames);
+    tls_builder.danger_accept_invalid_certs(builder.accept_invalid_certs);
+
+    let min_tls_version = match builder.min_tls_version {
+        MinTlsVersion::Tlsv10 => native_tls::Protocol::Tlsv10,
+        MinTlsVersion::Tlsv11 => native_tls::Protocol::Tlsv11,
+        MinTlsVersion::Tlsv12 => native_tls::Protocol::Tlsv12,
+    };
+
+    tls_builder.min_protocol_version(Some(min_tls_version));
+    if let Some(identity) = builder.identity {
+        tls_builder.identity(identity.0);
+    }
+
+    let connector = tls_builder.build().map_err(error::tls)?;
+    Ok((builder.server_name.into_boxed_str(), connector))
+}
+
+#[derive(Debug, Clone, Default)]
+#[allow(missing_copy_implementations)]
+#[non_exhaustive]
+pub(super) enum CertificateStore {
+    #[default]
+    System,
+    None,
+}
+
+#[derive(Clone)]
+pub(super) struct Certificate(pub(super) native_tls::Certificate);
+
+impl Certificate {
+    pub(super) fn from_pem(pem: &[u8]) -> Result<Self, Error> {
+        Ok(Self(
+            native_tls::Certificate::from_pem(pem).map_err(error::tls)?,
+        ))
+    }
+
+    pub(super) fn from_der(der: &[u8]) -> Result<Self, Error> {
+        Ok(Self(
+            native_tls::Certificate::from_der(der).map_err(error::tls)?,
+        ))
+    }
+}
+
+impl Debug for Certificate {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Certificate").finish_non_exhaustive()
+    }
+}
+
+#[derive(Clone)]
+pub(super) struct Identity(pub(super) native_tls::Identity);
+
+impl Identity {
+    pub(super) fn from_pem(pem: &[u8], key: &[u8]) -> Result<Self, Error> {
+        Ok(Self(
+            native_tls::Identity::from_pkcs8(pem, key).map_err(error::tls)?,
+        ))
+    }
+}
+
+impl Debug for Identity {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Identity").finish_non_exhaustive()
+    }
+}
+
+#[derive(Debug, Copy, Clone, Default)]
+#[non_exhaustive]
+pub(super) enum MinTlsVersion {
+    Tlsv10,
+    Tlsv11,
+    #[default]
+    Tlsv12,
+}
--- a/src/transport/smtp/client/tls/rustls.rs
+++ b/src/transport/smtp/client/tls/rustls.rs
@@ -0,0 +1,329 @@
+use std::{
+    fmt::{self, Debug},
+    sync::Arc,
+};
+
+use rustls::{
+    client::danger::{HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier},
+    crypto::{verify_tls12_signature, verify_tls13_signature, CryptoProvider},
+    pki_types::{self, UnixTime},
+    server::ParsedCertificate,
+    ClientConfig, DigitallySignedStruct, RootCertStore, SignatureScheme,
+};
+
+use crate::transport::smtp::error::{self, Error};
+
+pub(super) fn build_connector(
+    builder: super::TlsParametersBuilder<super::Rustls>,
+) -> Result<(ServerName, Arc<ClientConfig>), Error> {
+    let just_version3 = &[&rustls::version::TLS13];
+    let supported_versions = match builder.min_tls_version {
+        MinTlsVersion::Tlsv12 => rustls::ALL_VERSIONS,
+        MinTlsVersion::Tlsv13 => just_version3,
+    };
+
+    let crypto_provider = crate::rustls_crypto::crypto_provider();
+    let tls = ClientConfig::builder_with_provider(Arc::clone(&crypto_provider))
+        .with_protocol_versions(supported_versions)
+        .map_err(error::tls)?;
+
+    // Build TLS config
+    let mut root_cert_store = RootCertStore::empty();
+    #[cfg(feature = "rustls-platform-verifier")]
+    let mut extra_roots = Vec::new();
+
+    match builder.cert_store {
+        #[cfg(feature = "rustls-platform-verifier")]
+        CertificateStore::PlatformVerifier => {
+            extra_roots = builder
+                .root_certs
+                .iter()
+                .map(|cert| cert.0.clone())
+                .collect();
+        }
+        #[cfg(feature = "rustls-native-certs")]
+        CertificateStore::NativeCerts => {
+            let rustls_native_certs::CertificateResult { certs, errors, .. } =
+                rustls_native_certs::load_native_certs();
+            let errors_len = errors.len();
+
+            let (added, ignored) = root_cert_store.add_parsable_certificates(certs);
+            #[cfg(feature = "tracing")]
+            tracing::debug!(
+                "loaded platform certs with {errors_len} failing to load, {added} valid and {ignored} ignored (invalid) certs"
+            );
+            #[cfg(not(feature = "tracing"))]
+            let _ = (errors_len, added, ignored);
+        }
+        #[cfg(feature = "webpki-roots")]
+        CertificateStore::WebpkiRoots => {
+            root_cert_store.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
+        }
+        CertificateStore::None => {}
+    }
+    for cert in builder.root_certs {
+        root_cert_store.add(cert.0).map_err(error::tls)?;
+    }
+
+    let tls = match (
+        builder.cert_store,
+        builder.accept_invalid_certs,
+        builder.accept_invalid_hostnames,
+    ) {
+        #[cfg(feature = "rustls-platform-verifier")]
+        (CertificateStore::PlatformVerifier, false, _) => {
+            tls.dangerous().with_custom_certificate_verifier(Arc::new(
+                rustls_platform_verifier::Verifier::new_with_extra_roots(
+                    extra_roots,
+                    crypto_provider,
+                )
+                .map_err(error::tls)?,
+            ))
+        }
+        (_, true, _) | (_, _, true) => {
+            let verifier = InvalidCertsVerifier {
+                ignore_invalid_hostnames: builder.accept_invalid_hostnames,
+                ignore_invalid_certs: builder.accept_invalid_certs,
+                roots: root_cert_store,
+                crypto_provider,
+            };
+            tls.dangerous()
+                .with_custom_certificate_verifier(Arc::new(verifier))
+        }
+        _ => tls.with_root_certificates(root_cert_store),
+    };
+
+    let tls = if let Some(identity) = builder.identity {
+        tls.with_client_auth_cert(identity.chain, identity.key)
+            .map_err(error::tls)?
+    } else {
+        tls.with_no_client_auth()
+    };
+    let server_name = ServerName::try_from(builder.server_name)?;
+    Ok((server_name, Arc::new(tls)))
+}
+
+#[derive(Clone)]
+pub(in crate::transport::smtp) struct ServerName {
+    val: pki_types::ServerName<'static>,
+    str_val: Box<str>,
+}
+
+impl ServerName {
+    #[allow(dead_code)]
+    pub(in crate::transport::smtp) fn inner(self) -> pki_types::ServerName<'static> {
+        self.val
+    }
+
+    pub(in crate::transport::smtp) fn inner_ref(&self) -> &pki_types::ServerName<'static> {
+        &self.val
+    }
+
+    fn try_from(value: String) -> Result<Self, crate::transport::smtp::Error> {
+        let val: pki_types::ServerName<'_> = value
+            .as_str()
+            .try_into()
+            .map_err(crate::transport::smtp::error::tls)?;
+        Ok(Self {
+            val: val.to_owned(),
+            str_val: value.into_boxed_str(),
+        })
+    }
+}
+
+impl AsRef<str> for ServerName {
+    fn as_ref(&self) -> &str {
+        &self.str_val
+    }
+}
+
+#[derive(Debug, Clone, Default)]
+#[allow(dead_code, missing_copy_implementations)]
+#[non_exhaustive]
+pub(super) enum CertificateStore {
+    #[cfg(feature = "rustls-platform-verifier")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "rustls-platform-verifier")))]
+    #[cfg_attr(feature = "rustls-platform-verifier", default)]
+    PlatformVerifier,
+    #[cfg(feature = "rustls-native-certs")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "rustls-native-certs")))]
+    #[cfg_attr(
+        all(
+            not(feature = "rustls-platform-verifier"),
+            feature = "rustls-native-certs",
+        ),
+        default
+    )]
+    NativeCerts,
+    #[cfg(feature = "webpki-roots")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "webpki-roots")))]
+    #[cfg_attr(
+        all(
+            not(feature = "rustls-platform-verifier"),
+            not(feature = "rustls-native-certs"),
+            feature = "webpki-roots",
+        ),
+        default
+    )]
+    WebpkiRoots,
+    #[cfg_attr(
+        all(
+            not(feature = "webpki-roots"),
+            not(feature = "rustls-platform-verifier"),
+            not(feature = "rustls-native-certs")
+        ),
+        default
+    )]
+    None,
+}
+
+#[derive(Clone)]
+pub(super) struct Certificate(pub(super) pki_types::CertificateDer<'static>);
+
+impl Certificate {
+    #[allow(dead_code)]
+    pub(super) fn from_pem(pem: &[u8]) -> Result<Self, Error> {
+        use rustls::pki_types::pem::PemObject as _;
+
+        Ok(Self(
+            pki_types::CertificateDer::from_pem_slice(pem)
+                .map_err(|_| error::tls("invalid certificate"))?,
+        ))
+    }
+
+    pub(super) fn from_pem_bundle(pem: &[u8]) -> Result<Vec<Self>, Error> {
+        use rustls::pki_types::pem::PemObject as _;
+
+        pki_types::CertificateDer::pem_slice_iter(pem)
+            .map(|cert| Ok(Self(cert?)))
+            .collect::<Result<Vec<_>, pki_types::pem::Error>>()
+            .map_err(|_| error::tls("invalid certificate"))
+    }
+
+    pub(super) fn from_der(der: Vec<u8>) -> Self {
+        Self(der.into())
+    }
+}
+
+impl Debug for Certificate {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Certificate").finish_non_exhaustive()
+    }
+}
+
+pub(super) struct Identity {
+    pub(super) chain: Vec<pki_types::CertificateDer<'static>>,
+    pub(super) key: pki_types::PrivateKeyDer<'static>,
+}
+
+impl Identity {
+    pub(super) fn from_pem(pem: &[u8], key: &[u8]) -> Result<Self, Error> {
+        use rustls::pki_types::pem::PemObject as _;
+
+        let key = match pki_types::PrivateKeyDer::from_pem_slice(key) {
+            Ok(key) => key,
+            Err(pki_types::pem::Error::NoItemsFound) => {
+                return Err(error::tls("no private key found"))
+            }
+            Err(err) => return Err(error::tls(err)),
+        };
+
+        Ok(Self {
+            chain: vec![pem.to_owned().into()],
+            key,
+        })
+    }
+}
+
+impl Clone for Identity {
+    fn clone(&self) -> Self {
+        Self {
+            chain: self.chain.clone(),
+            key: self.key.clone_key(),
+        }
+    }
+}
+
+impl Debug for Identity {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Identity").finish_non_exhaustive()
+    }
+}
+
+#[derive(Debug, Copy, Clone, Default)]
+#[non_exhaustive]
+pub(super) enum MinTlsVersion {
+    #[default]
+    Tlsv12,
+    Tlsv13,
+}
+
+#[derive(Debug)]
+struct InvalidCertsVerifier {
+    ignore_invalid_hostnames: bool,
+    ignore_invalid_certs: bool,
+    roots: RootCertStore,
+    crypto_provider: Arc<CryptoProvider>,
+}
+
+impl ServerCertVerifier for InvalidCertsVerifier {
+    fn verify_server_cert(
+        &self,
+        end_entity: &pki_types::CertificateDer<'_>,
+        intermediates: &[pki_types::CertificateDer<'_>],
+        server_name: &pki_types::ServerName<'_>,
+        _ocsp_response: &[u8],
+        now: UnixTime,
+    ) -> Result<ServerCertVerified, rustls::Error> {
+        let cert = ParsedCertificate::try_from(end_entity)?;
+
+        if !self.ignore_invalid_certs {
+            rustls::client::verify_server_cert_signed_by_trust_anchor(
+                &cert,
+                &self.roots,
+                intermediates,
+                now,
+                self.crypto_provider.signature_verification_algorithms.all,
+            )?;
+        }
+
+        if !self.ignore_invalid_hostnames {
+            rustls::client::verify_server_name(&cert, server_name)?;
+        }
+        Ok(ServerCertVerified::assertion())
+    }
+
+    fn verify_tls12_signature(
+        &self,
+        message: &[u8],
+        cert: &pki_types::CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, rustls::Error> {
+        verify_tls12_signature(
+            message,
+            cert,
+            dss,
+            &self.crypto_provider.signature_verification_algorithms,
+        )
+    }
+
+    fn verify_tls13_signature(
+        &self,
+        message: &[u8],
+        cert: &pki_types::CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, rustls::Error> {
+        verify_tls13_signature(
+            message,
+            cert,
+            dss,
+            &self.crypto_provider.signature_verification_algorithms,
+        )
+    }
+
+    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
+        self.crypto_provider
+            .signature_verification_algorithms
+            .supported_schemes()
+    }
+}
--- a/src/transport/smtp/connection_url.rs
+++ b/src/transport/smtp/connection_url.rs
@@ -13,6 +13,7 @@ use super::{

 pub(crate) trait TransportBuilder {
    fn new<T: Into<String>>(server: T) -> Self;
+    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
    fn tls(self, tls: super::Tls) -> Self;
    fn port(self, port: u16) -> Self;
    fn credentials(self, credentials: Credentials) -> Self;
@@ -24,6 +25,7 @@ impl TransportBuilder for SmtpTransportBuilder {
        Self::new(server)
    }

+    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
    fn tls(self, tls: super::Tls) -> Self {
        self.tls(tls)
    }
@@ -47,6 +49,7 @@ impl TransportBuilder for AsyncSmtpTransportBuilder {
        Self::new(server)
    }

+    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
    fn tls(self, tls: super::Tls) -> Self {
        self.tls(tls)
    }
--- a/src/transport/smtp/error.rs
+++ b/src/transport/smtp/error.rs
@@ -77,6 +77,11 @@ impl Error {
        matches!(self.inner.kind, Kind::Tls)
    }

+    /// Returns true if the error is because the transport was shut down
+    pub fn is_transport_shutdown(&self) -> bool {
+        matches!(self.inner.kind, Kind::TransportShutdown)
+    }
+
    /// Returns the status code, if the error was generated from a response.
    pub fn status(&self) -> Option<Code> {
        match self.inner.kind {
@@ -111,6 +116,8 @@ pub(crate) enum Kind {
    )]
    #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
    Tls,
+    /// Transport shutdown error
+    TransportShutdown,
 }

 impl fmt::Debug for Error {
@@ -136,6 +143,7 @@ impl fmt::Display for Error {
            Kind::Connection => f.write_str("Connection error")?,
            #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
            Kind::Tls => f.write_str("tls error")?,
+            Kind::TransportShutdown => f.write_str("transport has been shut down")?,
            Kind::Transient(code) => {
                write!(f, "transient error ({code})")?;
            }
@@ -189,3 +197,7 @@ pub(crate) fn connection<E: Into<BoxError>>(e: E) -> Error {
 pub(crate) fn tls<E: Into<BoxError>>(e: E) -> Error {
    Error::new(Kind::Tls, Some(e))
 }
+
+pub(crate) fn transport_shutdown() -> Error {
+    Error::new::<BoxError>(Kind::TransportShutdown, None)
+}
--- a/src/transport/smtp/pool/async_impl.rs
+++ b/src/transport/smtp/pool/async_impl.rs
@@ -1,6 +1,5 @@
 use std::{
    fmt::{self, Debug},
-    mem,
    ops::{Deref, DerefMut},
    sync::{Arc, OnceLock},
    time::{Duration, Instant},
@@ -15,11 +14,15 @@ use super::{
    super::{client::AsyncSmtpConnection, Error},
    PoolConfig,
 };
-use crate::{executor::SpawnHandle, transport::smtp::async_transport::AsyncSmtpClient, Executor};
+use crate::{
+    executor::SpawnHandle,
+    transport::smtp::{async_transport::AsyncSmtpClient, error},
+    Executor,
+};

-pub struct Pool<E: Executor> {
+pub(crate) struct Pool<E: Executor> {
    config: PoolConfig,
-    connections: Mutex<Vec<ParkedConnection>>,
+    connections: Mutex<Option<Vec<ParkedConnection>>>,
    client: AsyncSmtpClient<E>,
    handle: OnceLock<E::Handle>,
 }
@@ -29,16 +32,16 @@ struct ParkedConnection {
    since: Instant,
 }

-pub struct PooledConnection<E: Executor> {
+pub(crate) struct PooledConnection<E: Executor> {
    conn: Option<AsyncSmtpConnection>,
    pool: Arc<Pool<E>>,
 }

 impl<E: Executor> Pool<E> {
-    pub fn new(config: PoolConfig, client: AsyncSmtpClient<E>) -> Arc<Self> {
+    pub(crate) fn new(config: PoolConfig, client: AsyncSmtpClient<E>) -> Arc<Self> {
        let pool = Arc::new(Self {
            config,
-            connections: Mutex::new(Vec::new()),
+            connections: Mutex::new(Some(Vec::new())),
            client,
            handle: OnceLock::new(),
        });
@@ -60,6 +63,10 @@ impl<E: Executor> Pool<E> {
                            #[allow(clippy::needless_collect)]
                            let (count, dropped) = {
                                let mut connections = pool.connections.lock().await;
+                                let Some(connections) = connections.as_mut() else {
+                                    // The transport was shut down
+                                    return;
+                                };

                                let to_drop = connections
                                    .iter()
@@ -92,6 +99,11 @@ impl<E: Executor> Pool<E> {
                                };

                                let mut connections = pool.connections.lock().await;
+                                let Some(connections) = connections.as_mut() else {
+                                    // The transport was shut down
+                                    return;
+                                };
+
                                connections.push(ParkedConnection::park(conn));

                                #[cfg(feature = "tracing")]
@@ -134,10 +146,25 @@ impl<E: Executor> Pool<E> {
        pool
    }

-    pub async fn connection(self: &Arc<Self>) -> Result<PooledConnection<E>, Error> {
+    pub(crate) async fn shutdown(&self) {
+        let connections = { self.connections.lock().await.take() };
+        if let Some(connections) = connections {
+            abort_concurrent(connections.into_iter().map(ParkedConnection::unpark)).await;
+        }
+
+        if let Some(handle) = self.handle.get() {
+            handle.shutdown().await;
+        }
+    }
+
+    pub(crate) async fn connection(self: &Arc<Self>) -> Result<PooledConnection<E>, Error> {
        loop {
            let conn = {
                let mut connections = self.connections.lock().await;
+                let Some(connections) = connections.as_mut() else {
+                    // The transport was shut down
+                    return Err(error::transport_shutdown());
+                };
                connections.pop()
            };

@@ -181,13 +208,20 @@ impl<E: Executor> Pool<E> {
            #[cfg(feature = "tracing")]
            tracing::debug!("recycling connection");

-            let mut connections = self.connections.lock().await;
-            if connections.len() >= self.config.max_size as usize {
-                drop(connections);
-                conn.abort().await;
+            let mut connections_guard = self.connections.lock().await;
+
+            if let Some(connections) = connections_guard.as_mut() {
+                if connections.len() >= self.config.max_size as usize {
+                    drop(connections_guard);
+                    conn.abort().await;
+                } else {
+                    let conn = ParkedConnection::park(conn);
+                    connections.push(conn);
+                }
            } else {
-                let conn = ParkedConnection::park(conn);
-                connections.push(conn);
+                // The pool has already been shut down
+                drop(connections_guard);
+                conn.abort().await;
            }
        }
    }
@@ -200,7 +234,13 @@ impl<E: Executor> Debug for Pool<E> {
            .field(
                "connections",
                &match self.connections.try_lock() {
-                    Some(connections) => format!("{} connections", connections.len()),
+                    Some(connections) => {
+                        if let Some(connections) = connections.as_ref() {
+                            format!("{} connections", connections.len())
+                        } else {
+                            "SHUT DOWN".to_owned()
+                        }
+                    }

                    None => "LOCKED".to_owned(),
                },
@@ -222,14 +262,16 @@ impl<E: Executor> Drop for Pool<E> {
        #[cfg(feature = "tracing")]
        tracing::debug!("dropping Pool");

-        let connections = mem::take(self.connections.get_mut());
+        let connections = self.connections.get_mut().take();
        let handle = self.handle.take();
        E::spawn(async move {
            if let Some(handle) = handle {
                handle.shutdown().await;
            }

-            abort_concurrent(connections.into_iter().map(ParkedConnection::unpark)).await;
+            if let Some(connections) = connections {
+                abort_concurrent(connections.into_iter().map(ParkedConnection::unpark)).await;
+            }
        });
    }
 }
--- a/src/transport/smtp/pool/mod.rs
+++ b/src/transport/smtp/pool/mod.rs
@@ -1,8 +1,8 @@
 use std::time::Duration;

 #[cfg(any(feature = "tokio1", feature = "async-std1"))]
-pub mod async_impl;
-pub mod sync_impl;
+pub(super) mod async_impl;
+pub(super) mod sync_impl;

 /// Configuration for a connection pool
 #[derive(Debug, Clone)]
--- a/src/transport/smtp/pool/sync_impl.rs
+++ b/src/transport/smtp/pool/sync_impl.rs
@@ -1,8 +1,7 @@
 use std::{
    fmt::{self, Debug},
-    mem,
    ops::{Deref, DerefMut},
-    sync::{Arc, Mutex, TryLockError},
+    sync::{mpsc, Arc, Mutex, TryLockError},
    thread,
    time::{Duration, Instant},
 };
@@ -11,11 +10,12 @@ use super::{
    super::{client::SmtpConnection, Error},
    PoolConfig,
 };
-use crate::transport::smtp::transport::SmtpClient;
+use crate::transport::smtp::{error, transport::SmtpClient};

-pub struct Pool {
+pub(crate) struct Pool {
    config: PoolConfig,
-    connections: Mutex<Vec<ParkedConnection>>,
+    connections: Mutex<Option<Vec<ParkedConnection>>>,
+    thread_terminator: mpsc::SyncSender<()>,
    client: SmtpClient,
 }

@@ -24,16 +24,19 @@ struct ParkedConnection {
    since: Instant,
 }

-pub struct PooledConnection {
+pub(crate) struct PooledConnection {
    conn: Option<SmtpConnection>,
    pool: Arc<Pool>,
 }

 impl Pool {
-    pub fn new(config: PoolConfig, client: SmtpClient) -> Arc<Self> {
+    pub(crate) fn new(config: PoolConfig, client: SmtpClient) -> Arc<Self> {
+        let (thread_tx, thread_rx) = mpsc::sync_channel(1);
+
        let pool = Arc::new(Self {
            config,
-            connections: Mutex::new(Vec::new()),
+            connections: Mutex::new(Some(Vec::new())),
+            thread_terminator: thread_tx,
            client,
        });

@@ -54,6 +57,10 @@ impl Pool {
                        #[allow(clippy::needless_collect)]
                        let (count, dropped) = {
                            let mut connections = pool.connections.lock().unwrap();
+                            let Some(connections) = connections.as_mut() else {
+                                // The transport was shut down
+                                return;
+                            };

                            let to_drop = connections
                                .iter()
@@ -86,6 +93,11 @@ impl Pool {
                            };

                            let mut connections = pool.connections.lock().unwrap();
+                            let Some(connections) = connections.as_mut() else {
+                                // The transport was shut down
+                                return;
+                            };
+
                            connections.push(ParkedConnection::park(conn));

                            #[cfg(feature = "tracing")]
@@ -110,7 +122,14 @@ impl Pool {
                        }

                        drop(pool);
-                        thread::sleep(idle_timeout);
+
+                        match thread_rx.recv_timeout(idle_timeout) {
+                            Ok(()) | Err(mpsc::RecvTimeoutError::Disconnected) => {
+                                // The transport was shut down
+                                return;
+                            }
+                            Err(mpsc::RecvTimeoutError::Timeout) => {}
+                        }
                    }
                })
                .expect("couldn't spawn the Pool thread");
@@ -119,10 +138,25 @@ impl Pool {
        pool
    }

-    pub fn connection(self: &Arc<Self>) -> Result<PooledConnection, Error> {
+    pub(crate) fn shutdown(&self) {
+        let connections = { self.connections.lock().unwrap().take() };
+        if let Some(connections) = connections {
+            for conn in connections {
+                conn.unpark().abort();
+            }
+        }
+
+        _ = self.thread_terminator.try_send(());
+    }
+
+    pub(crate) fn connection(self: &Arc<Self>) -> Result<PooledConnection, Error> {
        loop {
            let conn = {
                let mut connections = self.connections.lock().unwrap();
+                let Some(connections) = connections.as_mut() else {
+                    // The transport was shut down
+                    return Err(error::transport_shutdown());
+                };
                connections.pop()
            };

@@ -166,13 +200,20 @@ impl Pool {
            #[cfg(feature = "tracing")]
            tracing::debug!("recycling connection");

-            let mut connections = self.connections.lock().unwrap();
-            if connections.len() >= self.config.max_size as usize {
-                drop(connections);
-                conn.abort();
+            let mut connections_guard = self.connections.lock().unwrap();
+
+            if let Some(connections) = connections_guard.as_mut() {
+                if connections.len() >= self.config.max_size as usize {
+                    drop(connections_guard);
+                    conn.abort();
+                } else {
+                    let conn = ParkedConnection::park(conn);
+                    connections.push(conn);
+                }
            } else {
-                let conn = ParkedConnection::park(conn);
-                connections.push(conn);
+                // The pool has already been shut down
+                drop(connections_guard);
+                conn.abort();
            }
        }
    }
@@ -185,7 +226,13 @@ impl Debug for Pool {
            .field(
                "connections",
                &match self.connections.try_lock() {
-                    Ok(connections) => format!("{} connections", connections.len()),
+                    Ok(connections) => {
+                        if let Some(connections) = connections.as_ref() {
+                            format!("{} connections", connections.len())
+                        } else {
+                            "SHUT DOWN".to_owned()
+                        }
+                    }

                    Err(TryLockError::WouldBlock) => "LOCKED".to_owned(),
                    Err(TryLockError::Poisoned(_)) => "POISONED".to_owned(),
@@ -201,10 +248,11 @@ impl Drop for Pool {
        #[cfg(feature = "tracing")]
        tracing::debug!("dropping Pool");

-        let connections = mem::take(&mut *self.connections.get_mut().unwrap());
-        for conn in connections {
-            let mut conn = conn.unpark();
-            conn.abort();
+        if let Some(connections) = self.connections.get_mut().unwrap().take() {
+            for conn in connections {
+                let mut conn = conn.unpark();
+                conn.abort();
+            }
        }
    }
 }
--- a/src/transport/smtp/transport.rs
+++ b/src/transport/smtp/transport.rs
@@ -60,6 +60,11 @@ impl Transport for SmtpTransport {

        Ok(result)
    }
+
+    fn shutdown(&self) {
+        #[cfg(feature = "pool")]
+        self.inner.shutdown();
+    }
 }

 impl Debug for SmtpTransport {
@@ -172,7 +177,7 @@ impl SmtpTransport {
    /// a proper URL encoder, like the following cargo script:
    ///
    /// ```rust
-    /// # let _ = r#"
+    /// # const TOML: &str = r#"
    /// #!/usr/bin/env cargo
    ///
    /// //! ```cargo
@@ -369,7 +374,7 @@ impl SmtpTransportBuilder {

 /// Build client
 #[derive(Debug, Clone)]
-pub struct SmtpClient {
+pub(super) struct SmtpClient {
    info: SmtpInfo,
 }

@@ -377,7 +382,7 @@ impl SmtpClient {
    /// Creates a new connection directly usable to send emails
    ///
    /// Handles encryption and authentication
-    pub fn connection(&self) -> Result<SmtpConnection, Error> {
+    pub(super) fn connection(&self) -> Result<SmtpConnection, Error> {
        #[allow(clippy::match_single_binding)]
        let tls_parameters = match &self.info.tls {
            #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
--- a/src/transport/smtp/util.rs
+++ b/src/transport/smtp/util.rs
@@ -4,7 +4,7 @@ use std::fmt::{Display, Formatter, Result as FmtResult};

 /// Encode a string as xtext
 #[derive(Debug)]
-pub struct XText<'a>(pub &'a str);
+pub(crate) struct XText<'a>(pub(crate) &'a str);

 impl Display for XText<'_> {
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
--- a/src/transport/stub/mod.rs
+++ b/src/transport/stub/mod.rs
@@ -43,13 +43,11 @@
 use std::{
    error::Error as StdError,
    fmt,
-    sync::{Arc, Mutex as StdMutex},
+    sync::{Arc, Mutex},
 };

 #[cfg(any(feature = "tokio1", feature = "async-std1"))]
 use async_trait::async_trait;
-#[cfg(any(feature = "tokio1", feature = "async-std1"))]
-use futures_util::lock::Mutex as FuturesMutex;

 #[cfg(any(feature = "tokio1", feature = "async-std1"))]
 use crate::AsyncTransport;
@@ -72,7 +70,7 @@ impl StdError for Error {}
 #[derive(Debug, Clone)]
 pub struct StubTransport {
    response: Result<(), Error>,
-    message_log: Arc<StdMutex<Vec<(Envelope, String)>>>,
+    message_log: Arc<Mutex<Vec<(Envelope, String)>>>,
 }

 /// This transport logs messages and always returns the given response
@@ -81,7 +79,7 @@ pub struct StubTransport {
 #[cfg_attr(docsrs, doc(cfg(any(feature = "tokio1", feature = "async-std1"))))]
 pub struct AsyncStubTransport {
    response: Result<(), Error>,
-    message_log: Arc<FuturesMutex<Vec<(Envelope, String)>>>,
+    message_log: Arc<Mutex<Vec<(Envelope, String)>>>,
 }

 impl StubTransport {
@@ -89,7 +87,7 @@ impl StubTransport {
    pub fn new(response: Result<(), Error>) -> Self {
        Self {
            response,
-            message_log: Arc::new(StdMutex::new(vec![])),
+            message_log: Arc::new(Mutex::new(vec![])),
        }
    }

@@ -97,7 +95,7 @@ impl StubTransport {
    pub fn new_ok() -> Self {
        Self {
            response: Ok(()),
-            message_log: Arc::new(StdMutex::new(vec![])),
+            message_log: Arc::new(Mutex::new(vec![])),
        }
    }

@@ -105,7 +103,7 @@ impl StubTransport {
    pub fn new_error() -> Self {
        Self {
            response: Err(Error),
-            message_log: Arc::new(StdMutex::new(vec![])),
+            message_log: Arc::new(Mutex::new(vec![])),
        }
    }

@@ -124,7 +122,7 @@ impl AsyncStubTransport {
    pub fn new(response: Result<(), Error>) -> Self {
        Self {
            response,
-            message_log: Arc::new(FuturesMutex::new(vec![])),
+            message_log: Arc::new(Mutex::new(vec![])),
        }
    }

@@ -132,7 +130,7 @@ impl AsyncStubTransport {
    pub fn new_ok() -> Self {
        Self {
            response: Ok(()),
-            message_log: Arc::new(FuturesMutex::new(vec![])),
+            message_log: Arc::new(Mutex::new(vec![])),
        }
    }

@@ -140,14 +138,14 @@ impl AsyncStubTransport {
    pub fn new_error() -> Self {
        Self {
            response: Err(Error),
-            message_log: Arc::new(FuturesMutex::new(vec![])),
+            message_log: Arc::new(Mutex::new(vec![])),
        }
    }

    /// Return all logged messages sent using [`AsyncTransport::send_raw`]
    #[cfg(any(feature = "tokio1", feature = "async-std1"))]
    pub async fn messages(&self) -> Vec<(Envelope, String)> {
-        self.message_log.lock().await.clone()
+        self.message_log.lock().unwrap().clone()
    }
 }

@@ -173,7 +171,7 @@ impl AsyncTransport for AsyncStubTransport {
    async fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
        self.message_log
            .lock()
-            .await
+            .unwrap()
            .push((envelope.clone(), String::from_utf8_lossy(email).into()));
        self.response
    }
Author	SHA1	Message	Date
Paolo Barbolini	716d7baac2	regression	2025-06-02 11:40:45 +02:00
Paolo Barbolini	659b0b50b1	fix	2025-06-02 11:14:11 +02:00
Paolo Barbolini	f332439000	clippy	2025-06-02 11:09:21 +02:00
Paolo Barbolini	335cdea3f9	Merge branch 'master' into better-tls-parameters-builder	2025-06-02 11:05:59 +02:00
Paolo Barbolini	d3d8e24824	feat: add `rustls-platform-verifier` support (#1081 )	2025-06-02 10:43:17 +02:00
Paolo Barbolini	c4df9730aa	refactor(smtp/pool): remove duplicate abort_concurrent implementation (#1092 )	2025-05-24 16:37:54 +02:00
Paolo Barbolini	bfed19e6ad	refactor(stub): always use std Mutex (#1091 )	2025-05-24 14:34:09 +00:00
David Campbell	629967ac98	docs: use `Mailbox::new` rather than string parsing (#1090 )	2025-05-24 16:21:15 +02:00
Paolo Barbolini	06e381ec9c	Prepare v0.11.16 (#1089 )	2025-05-12 11:16:14 +02:00
Paolo Barbolini	d9ce9a6e47	chore: deprecate ungated TLS types _when_ no TLS backend is enabled (#1084 )	2025-05-11 09:36:47 +02:00
Paolo Barbolini	e892b55b6b	build(deps): upgrade webpki-roots to v1 (#1088 )	2025-05-06 12:37:39 +00:00
Paolo Barbolini	7642b2130e	simpler stuff	2025-05-02 08:54:34 +02:00
Paolo Barbolini	5a3f189e50	happy clippy	2025-05-02 08:51:24 +02:00
Paolo Barbolini	31b8f297ec	enum weirdness	2025-05-02 08:43:50 +02:00
Paolo Barbolini	3a6ab6f398	async-std again	2025-05-02 08:33:34 +02:00
Paolo Barbolini	7b8fc5a678	async-std	2025-05-02 08:30:37 +02:00
Paolo Barbolini	2b36935b1f	done	2025-05-02 08:29:20 +02:00
Paolo Barbolini	d31490a2a9	Make this all internal only for now	2025-05-02 07:20:20 +02:00
Paolo Barbolini	b7482f0232	examples	2025-05-02 05:47:53 +02:00
Paolo Barbolini	abc8cdf789	examples	2025-05-02 05:35:54 +02:00
Paolo Barbolini	81b233def4	warnings	2025-05-02 05:30:30 +02:00
Paolo Barbolini	e644a6c2d3	#[allow(missing_copy_implementations)]	2025-05-02 05:27:40 +02:00
Paolo Barbolini	0385ca3b19	deprecations	2025-05-02 05:26:18 +02:00
Paolo Barbolini	d114f9caf3	fix	2025-05-02 05:23:25 +02:00
Paolo Barbolini	785307b091	fix async-std	2025-05-02 05:22:03 +02:00
Paolo Barbolini	f16cbeec51	fixme	2025-05-02 05:19:39 +02:00
Paolo Barbolini	5cbe9ba283	Have the old builder use the new one underneath	2025-05-02 05:17:53 +02:00
Paolo Barbolini	2f4e36ac61	wip	2025-05-01 21:23:31 +02:00
Paolo Barbolini	610b72e93b	broken doc build	2025-05-01 20:37:51 +02:00
Paolo Barbolini	69b7c5500a	wip	2025-05-01 20:29:43 +02:00
Paolo Barbolini	63c5fcccfc	Start moving types over	2025-05-01 20:22:23 +02:00
Paolo Barbolini	b583aff36c	Move things	2025-05-01 19:42:30 +02:00
Paolo Barbolini	512c5e3ce8	wip	2025-05-01 19:02:13 +02:00
Paolo Barbolini	771d212198	build: gate `web-time` behind `cfg(target_arch = "wasm32")` (#1086 )	2025-05-01 18:32:26 +02:00
Paolo Barbolini	83ba93944d	docs: add missing `doc(cfg(...))` attributes (#1085 )	2025-05-01 18:16:40 +02:00
Paolo Barbolini	de3ab006e2	fix: feature gate internal `TransportBuilder::tls` to avoid recursive call site (#1083 )	2025-05-01 15:09:07 +02:00
Paolo Barbolini	9504b7f45c	refactor: cleanup internal `TlsParameters` and `(Async)NetworkStream` config (#1082 )	2025-05-01 14:00:56 +02:00
dependabot[bot]	c91b356a96	build(deps): bump tokio from 1.44.1 to 1.44.2 (#1080 ) Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.44.1 to 1.44.2. - [Release notes](https://github.com/tokio-rs/tokio/releases) - [Commits](https://github.com/tokio-rs/tokio/compare/tokio-1.44.1...tokio-1.44.2) --- updated-dependencies: - dependency-name: tokio dependency-version: 1.44.2 dependency-type: indirect ... Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>	2025-04-08 06:57:33 +02:00
dependabot[bot]	118c1ad47f	build(deps): bump openssl from 0.10.71 to 0.10.72 (#1079 ) Bumps [openssl](https://github.com/sfackler/rust-openssl) from 0.10.71 to 0.10.72. - [Release notes](https://github.com/sfackler/rust-openssl/releases) - [Commits](https://github.com/sfackler/rust-openssl/compare/openssl-v0.10.71...openssl-v0.10.72) --- updated-dependencies: - dependency-name: openssl dependency-version: 0.10.72 dependency-type: indirect ... Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>	2025-04-06 11:49:28 +02:00
Paolo Barbolini	8bf4d3a9c1	style: fix `clippy::io_other_error` (#1078 )	2025-04-03 10:28:06 +00:00
Paolo Barbolini	1fcff673ba	fix: remove `E: Clone` bound from `AsyncFileTransport` `Clone` impl (#1075 )	2025-04-03 08:05:39 +00:00
Paolo Barbolini	8c70c0cfb4	build(deps): upgrade semver compatible dependencies (#1076 )	2025-04-03 07:54:06 +00:00
Paolo Barbolini	63d8d30088	fix: let cannot be used for global variables (#1077 )	2025-04-03 09:50:06 +02:00
Paolo Barbolini	6c0be84817	Prepare v0.11.15 (#1070 )	2025-03-10 17:26:17 +01:00
Paolo Barbolini	6059cb04d6	build(deps): upgrade email-encoding to v0.4 (#1069 )	2025-03-09 07:22:20 +00:00
Paolo Barbolini	fdf0346556	style: fix `rustdoc::broken_intra_doc_links` (#1068 )	2025-03-09 07:55:15 +01:00
Paolo Barbolini	0f9455715c	build(deps): upgrade semver compatible locked dependencies (#1067 )	2025-03-08 11:52:38 +00:00
Popax21	0b3a1ed278	feat: add controlled shutdown methods (#1045 )	2025-03-08 12:43:05 +01:00
Paolo Barbolini	76bf68268f	build(deps): bump minimum supported serde to v1.0.110 (#1064 )	2025-03-04 13:06:17 +01:00
Paolo Barbolini	99a86c0fac	build(deps): bump minimum supported rustls to v0.23.18 (#1063 )	2025-03-04 12:55:43 +01:00
Paolo Barbolini	f0de9ef02c	style: deny `unreachable_pub` lint (#1058 )	2025-02-23 10:17:17 +01:00
Paolo Barbolini	b4ddcbdcfc	build: bump MSRV to 1.74 (#1060 )	2025-02-23 10:16:57 +01:00