Prepare v0.11.10 (#1002)

And then downgrades:

cargo update -p clap --precise 4.3.24
cargo update -p clap_lex --precise 0.5.0
cargo update -p anstyle --precise 1.0.2

.github/workflows/test.yml

@@ -13,16 +13,16 @@ env:
 
 jobs:
   rustfmt:
-    name: rustfmt / nightly-2023-06-22
+    name: rustfmt / nightly-2024-09-01
     runs-on: ubuntu-latest
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Install rust
         run: |
-          rustup default nightly-2023-06-22
+          rustup default nightly-2024-09-01
           rustup component add rustfmt
 
       - name: cargo fmt
@@ -34,7 +34,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Install rust
         run: |
@@ -50,7 +50,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Install rust
         run: rustup update --no-self-update stable
@@ -80,7 +80,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Install rust
         run: |
@@ -112,12 +112,6 @@ jobs:
       - name: Install dkimverify
         run: sudo apt -y install python3-dkim
 
-      - name: Work around early dependencies MSRV bump
-        run: |
-          cargo update -p anstyle --precise 1.0.2
-          cargo update -p clap --precise 4.3.24
-          cargo update -p clap_lex --precise 0.5.0
-
       - name: Test with no default features
         run: cargo test --no-default-features
 
@@ -134,7 +128,7 @@ jobs:
 #    name: Coverage
 #    runs-on: ubuntu-latest
 #    steps:
-#      - uses: actions/checkout@v2
+#      - uses: actions/checkout@v4
 #      - uses: actions-rs/toolchain@v1
 #        with:
 #          toolchain: nightly

CHANGELOG.md

@@ -1,3 +1,56 @@
+<a name="v0.11.10"></a>
+### v0.11.10 (2024-10-23)
+
+#### Bug fixes
+
+* Ignore disconnect errors when `pool` feature of SMTP transport is disabled ([#999])
+* Use case insensitive comparisons for matching login challenge requests ([#1000])
+
+[#999]: https://github.com/lettre/lettre/pull/999
+[#1000]: https://github.com/lettre/lettre/pull/1000
+
+<a name="v0.11.9"></a>
+### v0.11.9 (2024-09-13)
+
+#### Bug fixes
+
+* Fix feature gate for `accept_invalid_hostnames` for rustls ([#988])
+* Fix parsing `Mailbox` with trailing spaces ([#986])
+
+#### Misc
+
+* Bump `rustls-native-certs` to v0.8 ([#992])
+* Make getting started example in readme complete ([#990])
+
+[#988]: https://github.com/lettre/lettre/pull/988
+[#986]: https://github.com/lettre/lettre/pull/986
+[#990]: https://github.com/lettre/lettre/pull/990
+[#992]: https://github.com/lettre/lettre/pull/992
+
+<a name="v0.11.8"></a>
+### v0.11.8 (2024-09-03)
+
+#### Features
+
+* Add mTLS support ([#974])
+* Implement `accept_invalid_hostnames` for rustls ([#977])
+* Provide certificate chain for peer certificates when using `rustls` or `boring-tls` ([#976])
+
+#### Changes
+
+* Make `HeaderName` comparisons via `PartialEq` case insensitive ([#980])
+
+#### Misc
+
+* Fix clippy warnings ([#979])
+* Replace manual impl of `#[non_exhaustive]` for `InvalidHeaderName` ([#981])
+
+[#974]: https://github.com/lettre/lettre/pull/974
+[#976]: https://github.com/lettre/lettre/pull/976
+[#977]: https://github.com/lettre/lettre/pull/977
+[#980]: https://github.com/lettre/lettre/pull/980
+[#981]: https://github.com/lettre/lettre/pull/981
+
 <a name="v0.11.7"></a>
 ### v0.11.7 (2024-04-23)
 

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 = "0.11.7"
+version = "0.11.10"
 description = "Email client"
 readme = "README.md"
 homepage = "https://lettre.rs"
@@ -20,7 +20,7 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 chumsky = "0.9"
-idna = "0.5"
+idna = "1"
 tracing = { version = "0.1.16", default-features = false, features = ["std"], optional = true } # feature
 
 # builder
@@ -47,7 +47,8 @@ percent-encoding = { version = "2.3", optional = true }
 native-tls = { version = "0.2.5", optional = true } # feature
 rustls = { version = "0.23.5", default-features = false, features = ["ring", "logging", "std", "tls12"], optional = true }
 rustls-pemfile = { version = "2", optional = true }
-rustls-native-certs = { version = "0.7", optional = true }
+rustls-native-certs = { version = "0.8", optional = true }
+rustls-pki-types = { version = "1.7", optional = true }
 webpki-roots = { version = "0.26", optional = true }
 boring = { version = "4", optional = true }
 
@@ -58,7 +59,6 @@ async-trait = { version = "0.1", optional = true }
 
 ## async-std
 async-std = { version = "1.8", optional = true }
-#async-native-tls = { version = "0.3.3", optional = true }
 futures-rustls = { version = "0.26", default-features = false, features = ["logging", "tls12", "ring"], optional = true }
 
 ## tokio
@@ -108,13 +108,12 @@ smtp-transport = ["dep:base64", "dep:nom", "dep:socket2", "dep:url", "dep:percen
 
 pool = ["dep:futures-util"]
 
-rustls-tls = ["dep:webpki-roots", "dep:rustls", "dep:rustls-pemfile"]
+rustls-tls = ["dep:webpki-roots", "dep:rustls", "dep:rustls-pemfile", "dep:rustls-pki-types"]
 
 boring-tls = ["dep:boring"]
 
 # async
 async-std1 = ["dep:async-std", "dep:async-trait", "dep:futures-io", "dep:futures-util"]
-#async-std1-native-tls = ["async-std1", "native-tls", "dep:async-native-tls"]
 async-std1-rustls-tls = ["async-std1", "rustls-tls", "dep:futures-rustls"]
 tokio1 = ["dep:tokio1_crate", "dep:async-trait", "dep:futures-io", "dep:futures-util"]
 tokio1-native-tls = ["tokio1", "native-tls", "dep:tokio1_native_tls_crate"]
@@ -123,6 +122,9 @@ tokio1-boring-tls = ["tokio1", "boring-tls", "dep:tokio1_boring"]
 
 dkim = ["dep:base64", "dep:sha2", "dep:rsa", "dep:ed25519-dalek"]
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(lettre_ignore_tls_mismatch)'] }
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs", "--cfg", "lettre_ignore_tls_mismatch"]

README.md

@@ -28,8 +28,8 @@
 </div>
 
 <div align="center">
-  <a href="https://deps.rs/crate/lettre/0.11.7">
+  <a href="https://deps.rs/crate/lettre/0.11.10">
-    <img src="https://deps.rs/crate/lettre/0.11.7/status.svg"
+    <img src="https://deps.rs/crate/lettre/0.11.10/status.svg"
       alt="dependency status" />
   </a>
 </div>
@@ -71,27 +71,29 @@ use lettre::message::header::ContentType;
 use lettre::transport::smtp::authentication::Credentials;
 use lettre::{Message, SmtpTransport, Transport};
 
-let email = Message::builder()
+fn main() {
-    .from("NoBody <nobody@domain.tld>".parse().unwrap())
+    let email = Message::builder()
-    .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
+        .from("NoBody <nobody@domain.tld>".parse().unwrap())
-    .to("Hei <hei@domain.tld>".parse().unwrap())
+        .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
-    .subject("Happy new year")
+        .to("Hei <hei@domain.tld>".parse().unwrap())
-    .header(ContentType::TEXT_PLAIN)
+        .subject("Happy new year")
-    .body(String::from("Be happy!"))
+        .header(ContentType::TEXT_PLAIN)
-    .unwrap();
+        .body(String::from("Be happy!"))
+        .unwrap();
 
-let creds = Credentials::new("smtp_username".to_owned(), "smtp_password".to_owned());
+    let creds = Credentials::new("smtp_username".to_owned(), "smtp_password".to_owned());
 
-// Open a remote connection to gmail
+    // Open a remote connection to gmail
-let mailer = SmtpTransport::relay("smtp.gmail.com")
+    let mailer = SmtpTransport::relay("smtp.gmail.com")
-    .unwrap()
+        .unwrap()
-    .credentials(creds)
+        .credentials(creds)
-    .build();
+        .build();
 
-// Send the email
+    // Send the email
-match mailer.send(&email) {
+    match mailer.send(&email) {
-    Ok(_) => println!("Email sent successfully!"),
+        Ok(_) => println!("Email sent successfully!"),
-    Err(e) => panic!("Could not send email: {e:?}"),
+        Err(e) => panic!("Could not send email: {e:?}"),
+    }
 }
 ```
 

src/address/envelope.rs

@@ -14,11 +14,71 @@ pub struct Envelope {
     /// The envelope recipient's addresses
     ///
     /// This can not be empty.
+    #[cfg_attr(
+        feature = "serde",
+        serde(deserialize_with = "serde_forward_path::deserialize")
+    )]
     forward_path: Vec<Address>,
     /// The envelope sender address
     reverse_path: Option<Address>,
 }
 
+/// just like the default implementation to deserialize `Vec<Address>` but it
+/// forbids **de**serializing empty lists
+#[cfg(feature = "serde")]
+mod serde_forward_path {
+    use super::Address;
+    /// dummy type required for serde
+    /// see example: https://serde.rs/deserialize-map.html
+    struct CustomVisitor;
+    impl<'de> serde::de::Visitor<'de> for CustomVisitor {
+        type Value = Vec<Address>;
+
+        fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            formatter.write_str("a non-empty list of recipient addresses")
+        }
+
+        fn visit_seq<S>(self, mut access: S) -> Result<Self::Value, S::Error>
+        where
+            S: serde::de::SeqAccess<'de>,
+        {
+            let mut seq: Vec<Address> = Vec::with_capacity(access.size_hint().unwrap_or(0));
+            while let Some(key) = access.next_element()? {
+                seq.push(key);
+            }
+            if seq.is_empty() {
+                Err(serde::de::Error::invalid_length(seq.len(), &self))
+            } else {
+                Ok(seq)
+            }
+        }
+    }
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<Address>, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        deserializer.deserialize_seq(CustomVisitor {})
+    }
+
+    #[cfg(test)]
+    mod tests {
+        #[test]
+        fn deserializing_empty_recipient_list_returns_error() {
+            assert!(
+                serde_json::from_str::<crate::address::Envelope>(r#"{"forward_path": []}"#)
+                    .is_err()
+            );
+        }
+        #[test]
+        fn deserializing_non_empty_recipient_list_is_ok() {
+            serde_json::from_str::<crate::address::Envelope>(
+                r#"{ "forward_path": [ {"user":"foo", "domain":"example.com"} ] }"#,
+            )
+            .unwrap();
+        }
+    }
+}
+
 impl Envelope {
     /// Creates a new envelope, which may fail if `to` is empty.
     ///

src/executor.rs

@@ -230,7 +230,7 @@ impl Executor for AsyncStd1Executor {
     ) -> Result<AsyncSmtpConnection, Error> {
         #[allow(clippy::match_single_binding)]
         let tls_parameters = match tls {
-            #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+            #[cfg(feature = "async-std1-rustls-tls")]
             Tls::Wrapper(tls_parameters) => Some(tls_parameters.clone()),
             _ => None,
         };
@@ -243,7 +243,7 @@ impl Executor for AsyncStd1Executor {
         )
         .await?;
 
-        #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+        #[cfg(feature = "async-std1-rustls-tls")]
         match tls {
             Tls::Opportunistic(tls_parameters) => {
                 if conn.can_starttls() {

src/lib.rs

@@ -109,7 +109,7 @@
 //! [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/0.11.7")]
+#![doc(html_root_url = "https://docs.rs/crate/lettre/0.11.10")]
 #![doc(html_favicon_url = "https://lettre.rs/favicon.ico")]
 #![doc(html_logo_url = "https://avatars0.githubusercontent.com/u/15113230?v=4")]
 #![forbid(unsafe_code)]
@@ -174,21 +174,7 @@ mod compiletime_checks {
     If you'd like to use `boring-tls` make sure that the `rustls-tls` feature hasn't been enabled by mistake.
     Make sure to apply the same to any of your crate dependencies that use the `lettre` crate.");
 
-    /*
+    #[cfg(all(feature = "async-std1", feature = "native-tls",))]
-    #[cfg(all(
-        feature = "async-std1",
-        feature = "native-tls",
-        not(feature = "async-std1-native-tls")
-    ))]
-    compile_error!("Lettre is being built with the `async-std1` and the `native-tls` features, but the `async-std1-native-tls` feature hasn't been turned on.
-    If you'd like to use rustls make sure that the `native-tls` hasn't been enabled by mistake (you may need to import lettre without default features)
-    If you're building a library which depends on lettre import it without default features and enable just the features you need.");
-    */
-    #[cfg(all(
-        feature = "async-std1",
-        feature = "native-tls",
-        not(feature = "async-std1-native-tls")
-    ))]
     compile_error!("Lettre is being built with the `async-std1` and the `native-tls` features, but the async-std integration doesn't support native-tls yet.
 If you'd like to work on the issue please take a look at https://github.com/lettre/lettre/issues/576.
 If you were trying to opt into `rustls-tls` and did not activate `native-tls`, disable the default-features of lettre in `Cargo.toml` and manually add the required features.

src/message/header/mod.rs

@@ -124,22 +124,18 @@ impl Headers {
     }
 
     pub(crate) fn find_header(&self, name: &str) -> Option<&HeaderValue> {
-        self.headers
+        self.headers.iter().find(|value| name == value.name)
-            .iter()
-            .find(|value| name.eq_ignore_ascii_case(&value.name))
     }
 
     fn find_header_mut(&mut self, name: &str) -> Option<&mut HeaderValue> {
-        self.headers
+        self.headers.iter_mut().find(|value| name == value.name)
-            .iter_mut()
-            .find(|value| name.eq_ignore_ascii_case(&value.name))
     }
 
     fn find_header_index(&self, name: &str) -> Option<usize> {
         self.headers
             .iter()
             .enumerate()
-            .find(|(_i, value)| name.eq_ignore_ascii_case(&value.name))
+            .find(|(_i, value)| name == value.name)
             .map(|(i, _)| i)
     }
 }
@@ -161,18 +157,9 @@ impl Display for Headers {
 /// A possible error when converting a `HeaderName` from another type.
 // comes from `http` crate
 #[allow(missing_copy_implementations)]
-#[derive(Clone)]
+#[derive(Debug, Clone)]
-pub struct InvalidHeaderName {
+#[non_exhaustive]
-    _priv: (),
+pub struct InvalidHeaderName;
-}
-
-impl fmt::Debug for InvalidHeaderName {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("InvalidHeaderName")
-            // skip _priv noise
-            .finish()
-    }
-}
 
 impl fmt::Display for InvalidHeaderName {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -189,14 +176,11 @@ pub struct HeaderName(Cow<'static, str>);
 impl HeaderName {
     /// Creates a new header name
     pub fn new_from_ascii(ascii: String) -> Result<Self, InvalidHeaderName> {
-        if !ascii.is_empty()
+        if !ascii.is_empty() && ascii.len() <= 76 && ascii.is_ascii() && !ascii.contains([':', ' '])
-            && ascii.len() <= 76
-            && ascii.is_ascii()
-            && !ascii.contains(|c| c == ':' || c == ' ')
         {
             Ok(Self(Cow::Owned(ascii)))
         } else {
-            Err(InvalidHeaderName { _priv: () })
+            Err(InvalidHeaderName)
         }
     }
 
@@ -257,23 +241,19 @@ impl AsRef<str> for HeaderName {
 
 impl PartialEq<HeaderName> for HeaderName {
     fn eq(&self, other: &HeaderName) -> bool {
-        let s1: &str = self.as_ref();
+        self.eq_ignore_ascii_case(other)
-        let s2: &str = other.as_ref();
-        s1 == s2
     }
 }
 
 impl PartialEq<&str> for HeaderName {
     fn eq(&self, other: &&str) -> bool {
-        let s: &str = self.as_ref();
+        self.eq_ignore_ascii_case(other)
-        s == *other
     }
 }
 
 impl PartialEq<HeaderName> for &str {
     fn eq(&self, other: &HeaderName) -> bool {
-        let s: &str = other.as_ref();
+        self.eq_ignore_ascii_case(other)
-        *self == s
     }
 }
 
@@ -467,6 +447,60 @@ mod tests {
         let _ = HeaderName::new_from_ascii_str("");
     }
 
+    #[test]
+    fn headername_headername_eq() {
+        assert_eq!(
+            HeaderName::new_from_ascii_str("From"),
+            HeaderName::new_from_ascii_str("From")
+        );
+    }
+
+    #[test]
+    fn headername_str_eq() {
+        assert_eq!(HeaderName::new_from_ascii_str("From"), "From");
+    }
+
+    #[test]
+    fn str_headername_eq() {
+        assert_eq!("From", HeaderName::new_from_ascii_str("From"));
+    }
+
+    #[test]
+    fn headername_headername_eq_case_insensitive() {
+        assert_eq!(
+            HeaderName::new_from_ascii_str("From"),
+            HeaderName::new_from_ascii_str("from")
+        );
+    }
+
+    #[test]
+    fn headername_str_eq_case_insensitive() {
+        assert_eq!(HeaderName::new_from_ascii_str("From"), "from");
+    }
+
+    #[test]
+    fn str_headername_eq_case_insensitive() {
+        assert_eq!("from", HeaderName::new_from_ascii_str("From"));
+    }
+
+    #[test]
+    fn headername_headername_ne() {
+        assert_ne!(
+            HeaderName::new_from_ascii_str("From"),
+            HeaderName::new_from_ascii_str("To")
+        );
+    }
+
+    #[test]
+    fn headername_str_ne() {
+        assert_ne!(HeaderName::new_from_ascii_str("From"), "To");
+    }
+
+    #[test]
+    fn str_headername_ne() {
+        assert_ne!("From", HeaderName::new_from_ascii_str("To"));
+    }
+
     // names taken randomly from https://it.wikipedia.org/wiki/Pinco_Pallino
 
     #[test]

src/message/mailbox/parsers/rfc2822.rs

@@ -170,7 +170,9 @@ fn phrase() -> impl Parser<char, Vec<char>, Error = Cheap<char>> {
 // mailbox         =       name-addr / addr-spec
 pub(crate) fn mailbox() -> impl Parser<char, (Option<String>, (String, String)), Error = Cheap<char>>
 {
-    choice((name_addr(), addr_spec().map(|addr| (None, addr)))).then_ignore(end())
+    choice((name_addr(), addr_spec().map(|addr| (None, addr))))
+        .padded()
+        .then_ignore(end())
 }
 
 // name-addr       =       [display-name] angle-addr

src/message/mailbox/types.rs

@@ -556,6 +556,14 @@ mod test {
         );
     }
 
+    #[test]
+    fn parse_address_only_trim() {
+        assert_eq!(
+            " kayo@example.com ".parse(),
+            Ok(Mailbox::new(None, "kayo@example.com".parse().unwrap()))
+        );
+    }
+
     #[test]
     fn parse_address_with_name() {
         assert_eq!(
@@ -567,6 +575,17 @@ mod test {
         );
     }
 
+    #[test]
+    fn parse_address_with_name_trim() {
+        assert_eq!(
+            " K. <kayo@example.com> ".parse(),
+            Ok(Mailbox::new(
+                Some("K.".into()),
+                "kayo@example.com".parse().unwrap()
+            ))
+        );
+    }
+
     #[test]
     fn parse_address_with_empty_name() {
         assert_eq!(
@@ -578,7 +597,7 @@ mod test {
     #[test]
     fn parse_address_with_empty_name_trim() {
         assert_eq!(
-            " <kayo@example.com>".parse(),
+            " <kayo@example.com> ".parse(),
             Ok(Mailbox::new(None, "kayo@example.com".parse().unwrap()))
         );
     }

src/transport/mod.rs

@@ -12,7 +12,7 @@
 //!
 //! * a service from your Cloud or hosting provider
 //! * an email server ([MTA] for Mail Transfer Agent, like Postfix or Exchange), running either
-//! locally on your servers or accessible over the network
+//!   locally on your servers or accessible over the network
 //! * a dedicated external service, like Mailchimp, Mailgun, etc.
 //!
 //! In most cases, the best option is to:

src/transport/smtp/async_transport.rs

@@ -45,7 +45,7 @@ impl AsyncTransport for AsyncSmtpTransport<Tokio1Executor> {
         let result = conn.send(envelope, email).await?;
 
         #[cfg(not(feature = "pool"))]
-        conn.quit().await?;
+        conn.abort().await;
 
         Ok(result)
     }
@@ -82,7 +82,6 @@ where
     #[cfg(any(
         feature = "tokio1-native-tls",
         feature = "tokio1-rustls-tls",
-        feature = "async-std1-native-tls",
         feature = "async-std1-rustls-tls"
     ))]
     #[cfg_attr(
@@ -117,7 +116,6 @@ where
     #[cfg(any(
         feature = "tokio1-native-tls",
         feature = "tokio1-rustls-tls",
-        feature = "async-std1-native-tls",
         feature = "async-std1-rustls-tls"
     ))]
     #[cfg_attr(
@@ -353,7 +351,6 @@ impl AsyncSmtpTransportBuilder {
     #[cfg(any(
         feature = "tokio1-native-tls",
         feature = "tokio1-rustls-tls",
-        feature = "async-std1-native-tls",
         feature = "async-std1-rustls-tls"
     ))]
     #[cfg_attr(

src/transport/smtp/authentication.rs

@@ -98,13 +98,17 @@ impl Mechanism {
                 let decoded_challenge = challenge
                     .ok_or_else(|| error::client("This mechanism does expect a challenge"))?;
 
-                if ["User Name", "Username:", "Username", "User Name\0"]
+                if contains_ignore_ascii_case(
-                    .contains(&decoded_challenge)
+                    decoded_challenge,
-                {
+                    ["User Name", "Username:", "Username", "User Name\0"],
+                ) {
                     return Ok(credentials.authentication_identity.clone());
                 }
 
-                if ["Password", "Password:", "Password\0"].contains(&decoded_challenge) {
+                if contains_ignore_ascii_case(
+                    decoded_challenge,
+                    ["Password", "Password:", "Password\0"],
+                ) {
                     return Ok(credentials.secret.clone());
                 }
 
@@ -121,6 +125,15 @@ impl Mechanism {
     }
 }
 
+fn contains_ignore_ascii_case<'a>(
+    haystack: &str,
+    needles: impl IntoIterator<Item = &'a str>,
+) -> bool {
+    needles
+        .into_iter()
+        .any(|item| item.eq_ignore_ascii_case(haystack))
+}
+
 #[cfg(test)]
 mod test {
     use super::{Credentials, Mechanism};
@@ -155,6 +168,23 @@ mod test {
         assert!(mechanism.response(&credentials, None).is_err());
     }
 
+    #[test]
+    fn test_login_case_insensitive() {
+        let mechanism = Mechanism::Login;
+
+        let credentials = Credentials::new("alice".to_owned(), "wonderland".to_owned());
+
+        assert_eq!(
+            mechanism.response(&credentials, Some("username")).unwrap(),
+            "alice"
+        );
+        assert_eq!(
+            mechanism.response(&credentials, Some("password")).unwrap(),
+            "wonderland"
+        );
+        assert!(mechanism.response(&credentials, None).is_err());
+    }
+
     #[test]
     fn test_xoauth2() {
         let mechanism = Mechanism::Xoauth2;

src/transport/smtp/client/async_connection.rs

@@ -373,4 +373,10 @@ impl AsyncSmtpConnection {
     pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
         self.stream.get_ref().peer_certificate()
     }
+
+    /// All the X509 certificates of the chain (DER encoded)
+    #[cfg(any(feature = "rustls-tls", feature = "boring-tls"))]
+    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
+        self.stream.get_ref().certificate_chain()
+    }
 }

src/transport/smtp/client/async_net.rs

@@ -6,8 +6,6 @@ use std::{
     time::Duration,
 };
 
-#[cfg(feature = "async-std1-native-tls")]
-use async_native_tls::TlsStream as AsyncStd1TlsStream;
 #[cfg(feature = "async-std1")]
 use async_std::net::{TcpStream as AsyncStd1TcpStream, ToSocketAddrs as AsyncStd1ToSocketAddrs};
 use futures_io::{
@@ -36,7 +34,6 @@ use tokio1_rustls::client::TlsStream as Tokio1RustlsTlsStream;
     feature = "tokio1-native-tls",
     feature = "tokio1-rustls-tls",
     feature = "tokio1-boring-tls",
-    feature = "async-std1-native-tls",
     feature = "async-std1-rustls-tls"
 ))]
 use super::InnerTlsParameters;
@@ -86,9 +83,6 @@ enum InnerAsyncNetworkStream {
     #[cfg(feature = "async-std1")]
     AsyncStd1Tcp(AsyncStd1TcpStream),
     /// Encrypted Tokio 1.x TCP stream
-    #[cfg(feature = "async-std1-native-tls")]
-    AsyncStd1NativeTls(AsyncStd1TlsStream<AsyncStd1TcpStream>),
-    /// Encrypted Tokio 1.x TCP stream
     #[cfg(feature = "async-std1-rustls-tls")]
     AsyncStd1RustlsTls(AsyncStd1RustlsTlsStream<AsyncStd1TcpStream>),
     /// Can't be built
@@ -119,8 +113,6 @@ impl AsyncNetworkStream {
             InnerAsyncNetworkStream::Tokio1BoringTls(s) => s.get_ref().peer_addr(),
             #[cfg(feature = "async-std1")]
             InnerAsyncNetworkStream::AsyncStd1Tcp(s) => s.peer_addr(),
-            #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => s.get_ref().peer_addr(),
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => s.get_ref().0.peer_addr(),
             InnerAsyncNetworkStream::None => {
@@ -288,16 +280,13 @@ impl AsyncNetworkStream {
                     .map_err(error::connection)?;
                 Ok(())
             }
-            #[cfg(all(
+            #[cfg(all(feature = "async-std1", not(feature = "async-std1-rustls-tls")))]
-                feature = "async-std1",
-                not(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))
-            ))]
             InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
                 let _ = tls_parameters;
-                panic!("Trying to upgrade an AsyncNetworkStream without having enabled either the async-std1-native-tls or the async-std1-rustls-tls feature");
+                panic!("Trying to upgrade an AsyncNetworkStream without having enabled the async-std1-rustls-tls feature");
             }
 
-            #[cfg(any(feature = "async-std1-native-tls", feature = "async-std1-rustls-tls"))]
+            #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
                 // get owned TcpStream
                 let tcp_stream = mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);
@@ -385,11 +374,7 @@ impl AsyncNetworkStream {
     }
 
     #[allow(unused_variables)]
-    #[cfg(any(
+    #[cfg(feature = "async-std1-rustls-tls")]
-        feature = "async-std1-native-tls",
-        feature = "async-std1-rustls-tls",
-        feature = "async-std1-boring-tls"
-    ))]
     async fn upgrade_asyncstd1_tls(
         tcp_stream: AsyncStd1TcpStream,
         mut tls_parameters: TlsParameters,
@@ -400,22 +385,6 @@ impl AsyncNetworkStream {
             #[cfg(feature = "native-tls")]
             InnerTlsParameters::NativeTls(connector) => {
                 panic!("native-tls isn't supported with async-std yet. See https://github.com/lettre/lettre/pull/531#issuecomment-757893531");
-
-                /*
-                #[cfg(not(feature = "async-std1-native-tls"))]
-                panic!("built without the async-std1-native-tls feature");
-
-                #[cfg(feature = "async-std1-native-tls")]
-                return {
-                    use async_native_tls::TlsConnector;
-
-                    // TODO: fix
-                    let connector: TlsConnector = todo!();
-                    // let connector = TlsConnector::from(connector);
-                    let stream = connector.connect(&domain, tcp_stream).await?;
-                    Ok(InnerAsyncNetworkStream::AsyncStd1NativeTls(stream))
-                };
-                */
             }
             #[cfg(feature = "rustls-tls")]
             InnerTlsParameters::RustlsTls(config) => {
@@ -456,14 +425,54 @@ impl AsyncNetworkStream {
             InnerAsyncNetworkStream::Tokio1BoringTls(_) => true,
             #[cfg(feature = "async-std1")]
             InnerAsyncNetworkStream::AsyncStd1Tcp(_) => false,
-            #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(_) => true,
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(_) => true,
             InnerAsyncNetworkStream::None => false,
         }
     }
 
+    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
+        match &self.inner {
+            #[cfg(feature = "tokio1")]
+            InnerAsyncNetworkStream::Tokio1Tcp(_) => {
+                Err(error::client("Connection is not encrypted"))
+            }
+            #[cfg(feature = "tokio1-native-tls")]
+            InnerAsyncNetworkStream::Tokio1NativeTls(_) => panic!("Unsupported"),
+            #[cfg(feature = "tokio1-rustls-tls")]
+            InnerAsyncNetworkStream::Tokio1RustlsTls(stream) => Ok(stream
+                .get_ref()
+                .1
+                .peer_certificates()
+                .unwrap()
+                .iter()
+                .map(|c| c.to_vec())
+                .collect()),
+            #[cfg(feature = "tokio1-boring-tls")]
+            InnerAsyncNetworkStream::Tokio1BoringTls(stream) => Ok(stream
+                .ssl()
+                .peer_cert_chain()
+                .unwrap()
+                .iter()
+                .map(|c| c.to_der().map_err(error::tls))
+                .collect::<Result<Vec<_>, _>>()?),
+            #[cfg(feature = "async-std1")]
+            InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
+                Err(error::client("Connection is not encrypted"))
+            }
+            #[cfg(feature = "async-std1-rustls-tls")]
+            InnerAsyncNetworkStream::AsyncStd1RustlsTls(stream) => Ok(stream
+                .get_ref()
+                .1
+                .peer_certificates()
+                .unwrap()
+                .iter()
+                .map(|c| c.to_vec())
+                .collect()),
+            InnerAsyncNetworkStream::None => panic!("InnerNetworkStream::None must never be built"),
+        }
+    }
+
     pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
         match &self.inner {
             #[cfg(feature = "tokio1")]
@@ -498,8 +507,6 @@ impl AsyncNetworkStream {
             InnerAsyncNetworkStream::AsyncStd1Tcp(_) => {
                 Err(error::client("Connection is not encrypted"))
             }
-            #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(t) => panic!("Unsupported"),
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(stream) => Ok(stream
                 .get_ref()
@@ -559,8 +566,6 @@ impl FuturesAsyncRead for AsyncNetworkStream {
             }
             #[cfg(feature = "async-std1")]
             InnerAsyncNetworkStream::AsyncStd1Tcp(s) => Pin::new(s).poll_read(cx, buf),
-            #[cfg(feature = "async-std1-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_read(cx, buf),
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_read(cx, buf),
             InnerAsyncNetworkStream::None => {
@@ -588,8 +593,6 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
             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-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_write(cx, buf),
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_write(cx, buf),
             InnerAsyncNetworkStream::None => {
@@ -611,8 +614,6 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
             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-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_flush(cx),
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_flush(cx),
             InnerAsyncNetworkStream::None => {
@@ -634,8 +635,6 @@ impl FuturesAsyncWrite for AsyncNetworkStream {
             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-native-tls")]
-            InnerAsyncNetworkStream::AsyncStd1NativeTls(s) => Pin::new(s).poll_close(cx),
             #[cfg(feature = "async-std1-rustls-tls")]
             InnerAsyncNetworkStream::AsyncStd1RustlsTls(s) => Pin::new(s).poll_close(cx),
             InnerAsyncNetworkStream::None => {

src/transport/smtp/client/connection.rs

@@ -307,4 +307,10 @@ impl SmtpConnection {
     pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
         self.stream.get_ref().peer_certificate()
     }
+
+    /// All the X509 certificates of the chain (DER encoded)
+    #[cfg(any(feature = "rustls-tls", feature = "boring-tls"))]
+    pub fn certificate_chain(&self) -> Result<Vec<Vec<u8>>, Error> {
+        self.stream.get_ref().certificate_chain()
+    }
 }

src/transport/smtp/client/mod.rs

@@ -38,7 +38,7 @@ pub(super) use self::tls::InnerTlsParameters;
 pub use self::tls::TlsVersion;
 pub use self::{
     connection::SmtpConnection,
-    tls::{Certificate, CertificateStore, Tls, TlsParameters, TlsParametersBuilder},
+    tls::{Certificate, CertificateStore, Identity, Tls, TlsParameters, TlsParametersBuilder},
 };
 
 #[cfg(any(feature = "tokio1", feature = "async-std1"))]
@@ -139,7 +139,7 @@ mod test {
     }
 
     #[test]
-    #[cfg(feature = "log")]
+    #[cfg(feature = "tracing")]
     fn test_escape_crlf() {
         assert_eq!(escape_crlf("\r\n"), "<CRLF>");
         assert_eq!(escape_crlf("EHLO my_name\r\n"), "EHLO my_name<CRLF>");

src/transport/smtp/client/net.rs

@@ -223,6 +223,32 @@ impl NetworkStream {
         }
     }
 
+    #[cfg(any(feature = "rustls-tls", 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-tls")]
+            InnerNetworkStream::RustlsTls(stream) => Ok(stream
+                .conn
+                .peer_certificates()
+                .unwrap()
+                .iter()
+                .map(|c| c.to_vec())
+                .collect()),
+            #[cfg(feature = "boring-tls")]
+            InnerNetworkStream::BoringTls(stream) => Ok(stream
+                .ssl()
+                .peer_cert_chain()
+                .unwrap()
+                .iter()
+                .map(|c| c.to_der().map_err(error::tls))
+                .collect::<Result<Vec<_>, _>>()?),
+            InnerNetworkStream::None => panic!("InnerNetworkStream::None must never be built"),
+        }
+    }
+
     #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
     pub fn peer_certificate(&self) -> Result<Vec<u8>, Error> {
         match &self.inner {

src/transport/smtp/client/tls.rs

@@ -4,6 +4,7 @@ use std::{io, sync::Arc};
 
 #[cfg(feature = "boring-tls")]
 use boring::{
+    pkey::PKey,
     ssl::{SslConnector, SslVersion},
     x509::store::X509StoreBuilder,
 };
@@ -12,8 +13,10 @@ use native_tls::{Protocol, TlsConnector};
 #[cfg(feature = "rustls-tls")]
 use rustls::{
     client::danger::{HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier},
+    crypto::WebPkiSupportedAlgorithms,
     crypto::{verify_tls12_signature, verify_tls13_signature},
-    pki_types::{CertificateDer, ServerName, UnixTime},
+    pki_types::{CertificateDer, PrivateKeyDer, ServerName, UnixTime},
+    server::ParsedCertificate,
     ClientConfig, DigitallySignedStruct, Error as TlsError, RootCertStore, SignatureScheme,
 };
 
@@ -108,7 +111,7 @@ pub enum CertificateStore {
     /// 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 the system store if the `rustls-native-certs` feature is
+    /// For rustls, this will also use the system store if the `rustls-native-certs` feature is
     /// enabled, or will fall back to `webpki-roots`.
     ///
     /// The boring-tls backend uses the same logic as OpenSSL on all platforms.
@@ -139,6 +142,7 @@ pub struct TlsParametersBuilder {
     domain: String,
     cert_store: CertificateStore,
     root_certs: Vec<Certificate>,
+    identity: Option<Identity>,
     accept_invalid_hostnames: bool,
     accept_invalid_certs: bool,
     #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
@@ -152,6 +156,7 @@ impl TlsParametersBuilder {
             domain,
             cert_store: CertificateStore::Default,
             root_certs: Vec::new(),
+            identity: None,
             accept_invalid_hostnames: false,
             accept_invalid_certs: false,
             #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
@@ -167,12 +172,20 @@ impl TlsParametersBuilder {
 
     /// Add a custom root certificate
     ///
-    /// Can be used to safely connect to a server using a self signed certificate, for example.
+    /// Can be used to safely connect to a server using a self-signed certificate, for example.
     pub fn add_root_certificate(mut self, cert: Certificate) -> Self {
         self.root_certs.push(cert);
         self
     }
 
+    /// Add a client certificate
+    ///
+    /// Can be used to configure a client certificate to present to the server.
+    pub fn identify_with(mut self, identity: Identity) -> Self {
+        self.identity = Some(identity);
+        self
+    }
+
     /// Controls whether certificates with an invalid hostname are accepted
     ///
     /// Defaults to `false`.
@@ -184,10 +197,11 @@ impl TlsParametersBuilder {
     /// including those from other sites, are trusted.
     ///
     /// This method introduces significant vulnerabilities to man-in-the-middle attacks.
-    ///
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
-    /// Hostname verification can only be disabled with the `native-tls` TLS backend.
+    #[cfg_attr(
-    #[cfg(any(feature = "native-tls", feature = "boring-tls"))]
+        docsrs,
-    #[cfg_attr(docsrs, doc(cfg(any(feature = "native-tls", feature = "boring-tls"))))]
+        doc(cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls")))
+    )]
     pub fn dangerous_accept_invalid_hostnames(mut self, accept_invalid_hostnames: bool) -> Self {
         self.accept_invalid_hostnames = accept_invalid_hostnames;
         self
@@ -275,6 +289,10 @@ impl TlsParametersBuilder {
         };
 
         tls_builder.min_protocol_version(Some(min_tls_version));
+        if let Some(identity) = self.identity {
+            tls_builder.identity(identity.native_tls);
+        }
+
         let connector = tls_builder.build().map_err(error::tls)?;
         Ok(TlsParameters {
             connector: InnerTlsParameters::NativeTls(connector),
@@ -317,6 +335,15 @@ impl TlsParametersBuilder {
             }
         }
 
+        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,
@@ -352,51 +379,73 @@ impl TlsParametersBuilder {
         };
 
         let tls = ClientConfig::builder_with_protocol_versions(supported_versions);
+        let provider = rustls::crypto::CryptoProvider::get_default()
+            .cloned()
+            .unwrap_or_else(|| Arc::new(rustls::crypto::ring::default_provider()));
 
-        let tls = if self.accept_invalid_certs {
+        // Build TLS config
-            tls.dangerous()
+        let signature_algorithms = provider.signature_verification_algorithms;
-                .with_custom_certificate_verifier(Arc::new(InvalidCertsVerifier {}))
-        } else {
-            let mut root_cert_store = RootCertStore::empty();
 
-            #[cfg(feature = "rustls-native-certs")]
+        let mut root_cert_store = RootCertStore::empty();
-            fn load_native_roots(store: &mut RootCertStore) -> Result<(), Error> {
+
-                let native_certs = rustls_native_certs::load_native_certs().map_err(error::tls)?;
+        #[cfg(feature = "rustls-native-certs")]
-                let (added, ignored) = store.add_parsable_certificates(native_certs);
+        fn load_native_roots(store: &mut RootCertStore) -> Result<(), Error> {
-                #[cfg(feature = "tracing")]
+            let rustls_native_certs::CertificateResult { certs, errors, .. } =
-                tracing::debug!(
+                rustls_native_certs::load_native_certs();
-                    "loaded platform certs with {added} valid and {ignored} ignored (invalid) certs"
+            let errors_len = errors.len();
-                );
+
-                Ok(())
+            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"
+            );
+            Ok(())
+        }
+
+        #[cfg(feature = "rustls-tls")]
+        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(not(feature = "rustls-native-certs"))]
+                load_webpki_roots(&mut root_cert_store);
             }
-
             #[cfg(feature = "rustls-tls")]
-            fn load_webpki_roots(store: &mut RootCertStore) {
+            CertificateStore::WebpkiRoots => {
-                store.extend(webpki_roots::TLS_SERVER_ROOTS.iter().cloned());
+                load_webpki_roots(&mut root_cert_store);
-            }
-
-            match self.cert_store {
-                CertificateStore::Default => {
-                    #[cfg(feature = "rustls-native-certs")]
-                    load_native_roots(&mut root_cert_store)?;
-                    #[cfg(not(feature = "rustls-native-certs"))]
-                    load_webpki_roots(&mut root_cert_store);
-                }
-                #[cfg(feature = "rustls-tls")]
-                CertificateStore::WebpkiRoots => {
-                    load_webpki_roots(&mut root_cert_store);
-                }
-                CertificateStore::None => {}
-            }
-            for cert in self.root_certs {
-                for rustls_cert in cert.rustls {
-                    root_cert_store.add(rustls_cert).map_err(error::tls)?;
-                }
             }
+            CertificateStore::None => {}
+        }
+        for cert in self.root_certs {
+            for rustls_cert in cert.rustls {
+                root_cert_store.add(rustls_cert).map_err(error::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,
+                signature_algorithms,
+            };
+            tls.dangerous()
+                .with_custom_certificate_verifier(Arc::new(verifier))
+        } else {
             tls.with_root_certificates(root_cert_store)
         };
-        let tls = tls.with_no_client_auth();
+
+        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)),
@@ -461,7 +510,7 @@ impl TlsParameters {
     }
 }
 
-/// A client certificate that can be used with [`TlsParametersBuilder::add_root_certificate`]
+/// A certificate that can be used with [`TlsParametersBuilder::add_root_certificate`]
 #[derive(Clone)]
 #[allow(missing_copy_implementations)]
 pub struct Certificate {
@@ -528,20 +577,109 @@ impl Debug for Certificate {
     }
 }
 
+/// An identity that can be used with [`TlsParametersBuilder::identify_with`]
+#[allow(missing_copy_implementations)]
+pub struct Identity {
+    #[cfg(feature = "native-tls")]
+    native_tls: native_tls::Identity,
+    #[cfg(feature = "rustls-tls")]
+    rustls_tls: (Vec<CertificateDer<'static>>, PrivateKeyDer<'static>),
+    #[cfg(feature = "boring-tls")]
+    boring_tls: (boring::x509::X509, PKey<boring::pkey::Private>),
+}
+
+impl Debug for Identity {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Identity").finish()
+    }
+}
+
+impl Clone for Identity {
+    fn clone(&self) -> Self {
+        Identity {
+            #[cfg(feature = "native-tls")]
+            native_tls: self.native_tls.clone(),
+            #[cfg(feature = "rustls-tls")]
+            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-tls", 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)?,
+            #[cfg(feature = "rustls-tls")]
+            rustls_tls: Identity::from_pem_rustls_tls(pem, key)?,
+            #[cfg(feature = "boring-tls")]
+            boring_tls: Identity::from_pem_boring_tls(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-tls")]
+    fn from_pem_rustls_tls(
+        pem: &[u8],
+        key: &[u8],
+    ) -> Result<(Vec<CertificateDer<'static>>, PrivateKeyDer<'static>), Error> {
+        let mut key = key;
+        let key = rustls_pemfile::private_key(&mut key).unwrap().unwrap();
+        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-tls")]
 #[derive(Debug)]
-struct InvalidCertsVerifier;
+struct InvalidCertsVerifier {
+    ignore_invalid_hostnames: bool,
+    ignore_invalid_certs: bool,
+    roots: RootCertStore,
+    signature_algorithms: WebPkiSupportedAlgorithms,
+}
 
 #[cfg(feature = "rustls-tls")]
 impl ServerCertVerifier for InvalidCertsVerifier {
     fn verify_server_cert(
         &self,
-        _end_entity: &CertificateDer<'_>,
+        end_entity: &CertificateDer<'_>,
-        _intermediates: &[CertificateDer<'_>],
+        intermediates: &[CertificateDer<'_>],
-        _server_name: &ServerName<'_>,
+        server_name: &ServerName<'_>,
         _ocsp_response: &[u8],
-        _now: UnixTime,
+        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.signature_algorithms.all,
+            )?;
+        }
+
+        if !self.ignore_invalid_hostnames {
+            rustls::client::verify_server_name(&cert, server_name)?;
+        }
         Ok(ServerCertVerified::assertion())
     }
 

src/transport/smtp/transport.rs

@@ -32,7 +32,7 @@ impl Transport for SmtpTransport {
         let result = conn.send(envelope, email)?;
 
         #[cfg(not(feature = "pool"))]
-        conn.quit()?;
+        conn.abort();
 
         Ok(result)
     }