diff --git a/Cargo.lock b/Cargo.lock
index c19c202..68af36f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -123,6 +123,19 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "async-native-tls"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9343dc5acf07e79ff82d0c37899f079db3534d99f189a1837c8e549c99405bec"
+dependencies = [
+ "futures-util",
+ "native-tls",
+ "thiserror",
+ "tokio",
+ "url",
+]
+
 [[package]]
 name = "async-process"
 version = "2.3.0"
@@ -165,6 +178,7 @@ name = "async-smtp"
 version = "0.10.0"
 dependencies = [
  "anyhow",
+ "async-native-tls",
  "async-std",
  "base64",
  "criterion",
@@ -299,6 +313,15 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37b2a672a2cb129a2e41c10b1224bb368f9f37a2b16b612598138befd7b37eb5"
 
+[[package]]
+name = "cc"
+version = "1.1.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2e7962b54006dcfcc61cb72735f4d89bb97061dd6a7ed882ec6b8ee53714c6f"
+dependencies = [
+ "shlex",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.0"
@@ -325,6 +348,22 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "core-foundation"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91e195e091a93c46f7102ec7818a2aa394e1e1771c3ab4825963fa03e45afb8f"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
+[[package]]
+name = "core-foundation-sys"
+version = "0.8.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b"
+
 [[package]]
 name = "criterion"
 version = "0.3.6"
@@ -469,6 +508,30 @@ version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "486f806e73c5707928240ddc295403b1b93c96a02038563881c4a2fd84b81ac4"
 
+[[package]]
+name = "foreign-types"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6f339eb8adc052cd2ca78910fda869aefa38d22d5cb648e6485e4d3fc06f3b1"
+dependencies = [
+ "foreign-types-shared",
+]
+
+[[package]]
+name = "foreign-types-shared"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00b0228411908ca8685dba7fc2cdd70ec9990a6e753e89b6ac91a84c40fbaf4b"
+
+[[package]]
+name = "form_urlencoded"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e13624c2627564efccf4934284bdd98cbaa14e79b0b5a141218e507b3a823456"
+dependencies = [
+ "percent-encoding",
+]
+
 [[package]]
 name = "futures"
 version = "0.3.31"
@@ -622,6 +685,16 @@ version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
 
+[[package]]
+name = "idna"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "634d9b1461af396cad843f47fdba5597a4f9e6ddd4bfb6ff5d85028c25cb12f6"
+dependencies = [
+ "unicode-bidi",
+ "unicode-normalization",
+]
+
 [[package]]
 name = "itertools"
 version = "0.10.5"
@@ -715,6 +788,23 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "native-tls"
+version = "0.2.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8614eb2c83d59d1c8cc974dd3f920198647674a0a035e1af1fa58707e317466"
+dependencies = [
+ "libc",
+ "log",
+ "openssl",
+ "openssl-probe",
+ "openssl-sys",
+ "schannel",
+ "security-framework",
+ "security-framework-sys",
+ "tempfile",
+]
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -755,12 +845,62 @@ version = "11.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b410bbe7e14ab526a0e86877eb47c6996a2bd7746f027ba551028c925390e4e9"
 
+[[package]]
+name = "openssl"
+version = "0.10.68"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6174bc48f102d208783c2c84bf931bb75927a617866870de8a4ea85597f871f5"
+dependencies = [
+ "bitflags 2.6.0",
+ "cfg-if",
+ "foreign-types",
+ "libc",
+ "once_cell",
+ "openssl-macros",
+ "openssl-sys",
+]
+
+[[package]]
+name = "openssl-macros"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a948666b637a0f465e8564c73e89d4dde00d72d4d473cc972f390fc3dcee7d9c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.90",
+]
+
+[[package]]
+name = "openssl-probe"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ff011a302c396a5197692431fc1948019154afc178baf7d8e37367442a4601cf"
+
+[[package]]
+name = "openssl-sys"
+version = "0.9.104"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "45abf306cbf99debc8195b66b7346498d7b10c210de50418b5ccd7ceba08c741"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "parking"
 version = "2.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f38d5652c16fde515bb1ecef450ab0f6a219d619a7274976324d5e377f7dceba"
 
+[[package]]
+name = "percent-encoding"
+version = "2.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3148f5046208a5d56bcfc03053e3ca6334e51da8dfb19b6cdc8b306fae3283e"
+
 [[package]]
 name = "pin-project"
 version = "1.1.7"
@@ -804,6 +944,12 @@ dependencies = [
  "futures-io",
 ]
 
+[[package]]
+name = "pkg-config"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "953ec861398dccce10c670dfeaf3ec4911ca479e9c02154b3a215178c5f566f2"
+
 [[package]]
 name = "plotters"
 version = "0.3.7"
@@ -948,6 +1094,38 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "schannel"
+version = "0.1.26"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "01227be5826fa0690321a2ba6c5cd57a19cf3f6a09e76973b58e61de6ab9d1c1"
+dependencies = [
+ "windows-sys 0.59.0",
+]
+
+[[package]]
+name = "security-framework"
+version = "2.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c627723fd09706bacdb5cf41499e95098555af3c3c29d014dc3c458ef6be11c0"
+dependencies = [
+ "bitflags 2.6.0",
+ "core-foundation",
+ "core-foundation-sys",
+ "libc",
+ "security-framework-sys",
+]
+
+[[package]]
+name = "security-framework-sys"
+version = "2.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea4a292869320c0272d7bc55a5a6aafaff59b4f63404a003887b679a2e05b4b6"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.215"
@@ -990,6 +1168,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "shlex"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.2"
@@ -1040,6 +1224,19 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04cbcdd0c794ebb0d4cf35e88edd2f7d2c4c3e9a5a6dab322839b321c6a87a64"
+dependencies = [
+ "cfg-if",
+ "fastrand",
+ "once_cell",
+ "rustix",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "termcolor"
 version = "1.4.1"
@@ -1088,6 +1285,21 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "tinyvec"
+version = "1.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "445e881f4f6d382d5f27c034e25eb92edd7c784ceab92a0937db7f2e9471b938"
+dependencies = [
+ "tinyvec_macros",
+]
+
+[[package]]
+name = "tinyvec_macros"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1f3ccbac311fea05f86f61904b462b55fb3df8837a366dfc601a0161d0532f20"
+
 [[package]]
 name = "tokio"
 version = "1.41.1"
@@ -1131,24 +1343,56 @@ version = "0.1.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e672c95779cf947c5311f83787af4fa8fffd12fb27e4993211a84bdfd9610f9c"
 
+[[package]]
+name = "unicode-bidi"
+version = "0.3.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ab17db44d7388991a428b2ee655ce0c212e862eff1768a455c58f9aad6e7893"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "adb9e6ca4f869e1180728b7950e35922a7fc6397f7b641499e8f3ef06e50dc83"
 
+[[package]]
+name = "unicode-normalization"
+version = "0.1.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5033c97c4262335cded6d6fc3e5c18ab755e1a3dc96376350f3d8e9f009ad956"
+dependencies = [
+ "tinyvec",
+]
+
 [[package]]
 name = "unicode-width"
 version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7dd6e30e90baa6f72411720665d41d89b9a3d039dc45b8faea1ddd07f617f6af"
 
+[[package]]
+name = "url"
+version = "2.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22784dbdf76fdde8af1aeda5622b546b422b6fc585325248a2bf9f5e41e94d6c"
+dependencies = [
+ "form_urlencoded",
+ "idna",
+ "percent-encoding",
+]
+
 [[package]]
 name = "value-bag"
 version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3ef4c4aa54d5d05a279399bfa921ec387b7aba77caf7a682ae8d86785b8fdad2"
 
+[[package]]
+name = "vcpkg"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"
diff --git a/Cargo.toml b/Cargo.toml
index 9fa49bc..8eab071 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,6 +28,7 @@ thiserror = "1"
 tokio = { version = "1", default-features = false, features = ["time", "io-util"], optional = true }
 
 [dev-dependencies]
+async-native-tls = { version = "0.5", default-features = false }
 env_logger = "^0.9"
 glob = "^0.3"
 criterion = "^0.3"
@@ -39,7 +40,17 @@ name = "send"
 path = "examples/send.rs"
 required-features = ["runtime-tokio"]
 
+[[example]]
+name = "ssl-xoauth2"
+path = "examples/ssl-xoauth2.rs"
+required-features = ["runtime-tokio"]
+
+[[example]]
+name = "starttls-xoauth2"
+path = "examples/starttls-xoauth2.rs"
+required-features = ["runtime-tokio"]
+
 [features]
 default = ["runtime-tokio"]
-runtime-async-std = ["async-std"]
-runtime-tokio = ["tokio"]
+runtime-async-std = ["async-std", "async-native-tls/runtime-async-std"]
+runtime-tokio = ["tokio", "async-native-tls/runtime-tokio"]
diff --git a/examples/ssl-xoauth2.rs b/examples/ssl-xoauth2.rs
new file mode 100644
index 0000000..9dc978b
--- /dev/null
+++ b/examples/ssl-xoauth2.rs
@@ -0,0 +1,43 @@
+// this example can be used as a reference for other smtp providers
+// tested with gmail smtp server
+
+use async_native_tls::TlsConnector;
+use async_smtp::authentication::{Credentials, Mechanism};
+use async_smtp::{Envelope, SendableEmail, SmtpClient, SmtpTransport};
+use tokio::io::BufStream;
+use tokio::net::TcpStream;
+
+pub type Error = Box<dyn std::error::Error + Send + Sync>;
+pub type Result<T> = std::result::Result<T, Error>;
+
+// https://developers.google.com/gmail/imap/imap-smtp
+const SMTP_SERVER: &str = "smtp.gmail.com";
+const SSL_PORT: u16 = 465;
+
+const USER: &str = "user@gmail.com";
+const ACCESS_TOKEN: &str = "accesstoken";
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let stream = TcpStream::connect((SMTP_SERVER, SSL_PORT)).await?;
+    let tls_stream = TlsConnector::new().connect(SMTP_SERVER, stream).await?;
+
+    let client = SmtpClient::new();
+    let mut transport = SmtpTransport::new(client, BufStream::new(tls_stream)).await?;
+
+    let credentials = Credentials::new(USER.to_owned(), ACCESS_TOKEN.to_owned());
+    transport
+        .auth(Mechanism::Xoauth2, &credentials) // use modern auth mechanism
+        .await?;
+
+    let email = SendableEmail::new(
+        Envelope::new(
+            Some(USER.parse().unwrap()),
+            vec!["root@localhost".parse().unwrap()],
+        )?,
+        "Hello world",
+    );
+    transport.send(email).await?;
+
+    Ok(())
+}
diff --git a/examples/starttls-xoauth2.rs b/examples/starttls-xoauth2.rs
new file mode 100644
index 0000000..84844da
--- /dev/null
+++ b/examples/starttls-xoauth2.rs
@@ -0,0 +1,50 @@
+// this example can be used as a reference for other smtp providers
+// tested with gmail, outlook smtp servers
+
+use async_native_tls::TlsConnector;
+use async_smtp::authentication::{Credentials, Mechanism};
+use async_smtp::{Envelope, SendableEmail, SmtpClient, SmtpTransport};
+use tokio::io::BufStream;
+use tokio::net::TcpStream;
+
+pub type Error = Box<dyn std::error::Error + Send + Sync>;
+pub type Result<T> = std::result::Result<T, Error>;
+
+// https://developers.google.com/gmail/imap/imap-smtp
+const SMTP_SERVER: &str = "smtp.gmail.com";
+const TLS_PORT: u16 = 587;
+
+const USER: &str = "user@gmail.com";
+const ACCESS_TOKEN: &str = "accesstoken";
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let stream = BufStream::new(TcpStream::connect((SMTP_SERVER, TLS_PORT)).await?);
+
+    let client = SmtpClient::new();
+    let transport = SmtpTransport::new(client, stream).await?;
+
+    let pre_tls_stream = transport.starttls().await?.into_inner();
+    let tls_stream = TlsConnector::new()
+        .connect(SMTP_SERVER, pre_tls_stream)
+        .await?;
+
+    let client = SmtpClient::new().without_greeting(); // do not wait an greeting message after STARTTLS
+    let mut transport = SmtpTransport::new(client, BufStream::new(tls_stream)).await?;
+
+    let credentials = Credentials::new(USER.to_owned(), ACCESS_TOKEN.to_owned());
+    transport
+        .auth(Mechanism::Xoauth2, &credentials) // use modern auth mechanism
+        .await?;
+
+    let email = SendableEmail::new(
+        Envelope::new(
+            Some(USER.parse().unwrap()),
+            vec!["root@localhost".parse().unwrap()],
+        )?,
+        "Hello world",
+    );
+    transport.send(email).await?;
+
+    Ok(())
+}