diff --git a/src/transport/smtp/mod.rs b/src/transport/smtp/mod.rs
index 75a80e7..619b8d9 100644
--- a/src/transport/smtp/mod.rs
+++ b/src/transport/smtp/mod.rs
@@ -178,22 +178,16 @@
 
 use std::time::Duration;
 
-#[cfg(feature = "r2d2")]
-use r2d2::{Builder, Pool};
-
+pub use self::transport::{SmtpClient, SmtpTransport, SmtpTransportBuilder};
 #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
 use crate::transport::smtp::client::TlsParameters;
-use crate::{
-    transport::smtp::{
-        authentication::{Credentials, Mechanism, DEFAULT_MECHANISMS},
-        client::SmtpConnection,
-        error::Error,
-        extension::ClientId,
-        response::Response,
-    },
-    Envelope, Transport,
+use crate::transport::smtp::{
+    authentication::{Credentials, Mechanism, DEFAULT_MECHANISMS},
+    client::SmtpConnection,
+    error::Error,
+    extension::ClientId,
+    response::Response,
 };
-
 use client::Tls;
 
 pub mod authentication;
@@ -204,6 +198,7 @@ pub mod extension;
 #[cfg(feature = "r2d2")]
 pub mod pool;
 pub mod response;
+mod transport;
 pub mod util;
 
 // Registered port numbers:
@@ -222,72 +217,6 @@ pub const SUBMISSIONS_PORT: u16 = 465;
 /// Default timeout
 pub const DEFAULT_TIMEOUT: Duration = Duration::from_secs(60);
 
-#[allow(missing_debug_implementations)]
-#[derive(Clone)]
-pub struct SmtpTransport {
-    #[cfg(feature = "r2d2")]
-    inner: Pool<SmtpClient>,
-    #[cfg(not(feature = "r2d2"))]
-    inner: SmtpClient,
-}
-
-impl Transport for SmtpTransport {
-    type Ok = Response;
-    type Error = Error;
-
-    /// Sends an email
-    fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
-        #[cfg(feature = "r2d2")]
-        let mut conn = self.inner.get()?;
-        #[cfg(not(feature = "r2d2"))]
-        let mut conn = self.inner.connection()?;
-
-        let result = conn.send(envelope, email)?;
-
-        #[cfg(not(feature = "r2d2"))]
-        conn.quit()?;
-
-        Ok(result)
-    }
-}
-
-impl SmtpTransport {
-    /// Simple and secure transport, should be used when possible.
-    /// Creates an encrypted transport over submissions port, using the provided domain
-    /// to validate TLS certificates.
-    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
-    pub fn relay(relay: &str) -> Result<SmtpTransportBuilder, Error> {
-        let tls_parameters = TlsParameters::new(relay.into())?;
-
-        Ok(Self::builder_dangerous(relay)
-            .port(SUBMISSIONS_PORT)
-            .tls(Tls::Wrapper(tls_parameters)))
-    }
-
-    /// Creates a new local SMTP client to port 25
-    ///
-    /// Shortcut for local unencrypted relay (typical local email daemon that will handle relaying)
-    pub fn unencrypted_localhost() -> SmtpTransport {
-        Self::builder_dangerous("localhost").build()
-    }
-
-    /// Creates a new SMTP client
-    ///
-    /// Defaults are:
-    ///
-    /// * No authentication
-    /// * No TLS
-    /// * A 60 seconds timeout for smtp commands
-    /// * Port 25
-    ///
-    /// Consider using [`SmtpTransport::relay`] instead, if possible.
-    pub fn builder_dangerous<T: Into<String>>(server: T) -> SmtpTransportBuilder {
-        let mut new = SmtpInfo::default();
-        new.server = server.into();
-        SmtpTransportBuilder { info: new }
-    }
-}
-
 #[allow(missing_debug_implementations)]
 #[derive(Clone)]
 struct SmtpInfo {
@@ -321,122 +250,3 @@ impl Default for SmtpInfo {
         }
     }
 }
-
-/// Contains client configuration
-#[allow(missing_debug_implementations)]
-#[derive(Clone)]
-pub struct SmtpTransportBuilder {
-    info: SmtpInfo,
-}
-
-/// Builder for the SMTP `SmtpTransport`
-impl SmtpTransportBuilder {
-    /// Set the name used during EHLO
-    pub fn hello_name(mut self, name: ClientId) -> Self {
-        self.info.hello_name = name;
-        self
-    }
-
-    /// Set the authentication mechanism to use
-    pub fn credentials(mut self, credentials: Credentials) -> Self {
-        self.info.credentials = Some(credentials);
-        self
-    }
-
-    /// Set the authentication mechanism to use
-    pub fn authentication(mut self, mechanisms: Vec<Mechanism>) -> Self {
-        self.info.authentication = mechanisms;
-        self
-    }
-
-    /// Set the timeout duration
-    pub fn timeout(mut self, timeout: Option<Duration>) -> Self {
-        self.info.timeout = timeout;
-        self
-    }
-
-    /// Set the port to use
-    pub fn port(mut self, port: u16) -> Self {
-        self.info.port = port;
-        self
-    }
-
-    /// Set the TLS settings to use
-    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
-    pub fn tls(mut self, tls: Tls) -> Self {
-        self.info.tls = tls;
-        self
-    }
-
-    /// Build the client
-    fn build_client(self) -> SmtpClient {
-        SmtpClient { info: self.info }
-    }
-
-    /// Build the transport with custom pool settings
-    #[cfg(feature = "r2d2")]
-    pub fn build_with_pool(self, pool: Builder<SmtpClient>) -> SmtpTransport {
-        let pool = pool.build_unchecked(self.build_client());
-        SmtpTransport { inner: pool }
-    }
-
-    /// Build the transport (with default pool if enabled)
-    pub fn build(self) -> SmtpTransport {
-        let client = self.build_client();
-        SmtpTransport {
-            #[cfg(feature = "r2d2")]
-            inner: Pool::builder().max_size(5).build_unchecked(client),
-            #[cfg(not(feature = "r2d2"))]
-            inner: client,
-        }
-    }
-}
-
-/// Build client
-#[derive(Clone)]
-pub struct SmtpClient {
-    info: SmtpInfo,
-}
-
-impl SmtpClient {
-    /// Creates a new connection directly usable to send emails
-    ///
-    /// Handles encryption and authentication
-    pub fn connection(&self) -> Result<SmtpConnection, Error> {
-        let mut conn = SmtpConnection::connect::<(&str, u16)>(
-            (self.info.server.as_ref(), self.info.port),
-            self.info.timeout,
-            &self.info.hello_name,
-            #[allow(clippy::match_single_binding)]
-            match self.info.tls {
-                #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
-                Tls::Wrapper(ref tls_parameters) => Some(tls_parameters),
-                _ => None,
-            },
-        )?;
-
-        #[allow(clippy::match_single_binding)]
-        match self.info.tls {
-            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
-            Tls::Opportunistic(ref tls_parameters) => {
-                if conn.can_starttls() {
-                    conn.starttls(tls_parameters, &self.info.hello_name)?;
-                }
-            }
-            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
-            Tls::Required(ref tls_parameters) => {
-                conn.starttls(tls_parameters, &self.info.hello_name)?;
-            }
-            _ => (),
-        }
-
-        match &self.info.credentials {
-            Some(credentials) => {
-                conn.auth(self.info.authentication.as_slice(), &credentials)?;
-            }
-            None => (),
-        }
-
-        Ok(conn)
-    }
-}
diff --git a/src/transport/smtp/transport.rs b/src/transport/smtp/transport.rs
new file mode 100644
index 0000000..e2da184
--- /dev/null
+++ b/src/transport/smtp/transport.rs
@@ -0,0 +1,195 @@
+use std::time::Duration;
+
+#[cfg(feature = "r2d2")]
+use r2d2::{Builder, Pool};
+
+use super::{
+    ClientId, Credentials, Error, Mechanism, Response, SmtpConnection, SmtpInfo, Tls,
+    TlsParameters, SUBMISSIONS_PORT,
+};
+use crate::{Envelope, Transport};
+
+#[allow(missing_debug_implementations)]
+#[derive(Clone)]
+pub struct SmtpTransport {
+    #[cfg(feature = "r2d2")]
+    inner: Pool<SmtpClient>,
+    #[cfg(not(feature = "r2d2"))]
+    inner: SmtpClient,
+}
+
+impl Transport for SmtpTransport {
+    type Ok = Response;
+    type Error = Error;
+
+    /// Sends an email
+    fn send_raw(&self, envelope: &Envelope, email: &[u8]) -> Result<Self::Ok, Self::Error> {
+        #[cfg(feature = "r2d2")]
+        let mut conn = self.inner.get()?;
+        #[cfg(not(feature = "r2d2"))]
+        let mut conn = self.inner.connection()?;
+
+        let result = conn.send(envelope, email)?;
+
+        #[cfg(not(feature = "r2d2"))]
+        conn.quit()?;
+
+        Ok(result)
+    }
+}
+
+impl SmtpTransport {
+    /// Simple and secure transport, should be used when possible.
+    /// Creates an encrypted transport over submissions port, using the provided domain
+    /// to validate TLS certificates.
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    pub fn relay(relay: &str) -> Result<SmtpTransportBuilder, Error> {
+        let tls_parameters = TlsParameters::new(relay.into())?;
+
+        Ok(Self::builder_dangerous(relay)
+            .port(SUBMISSIONS_PORT)
+            .tls(Tls::Wrapper(tls_parameters)))
+    }
+
+    /// Creates a new local SMTP client to port 25
+    ///
+    /// Shortcut for local unencrypted relay (typical local email daemon that will handle relaying)
+    pub fn unencrypted_localhost() -> SmtpTransport {
+        Self::builder_dangerous("localhost").build()
+    }
+
+    /// Creates a new SMTP client
+    ///
+    /// Defaults are:
+    ///
+    /// * No authentication
+    /// * No TLS
+    /// * A 60 seconds timeout for smtp commands
+    /// * Port 25
+    ///
+    /// Consider using [`SmtpTransport::relay`] instead, if possible.
+    pub fn builder_dangerous<T: Into<String>>(server: T) -> SmtpTransportBuilder {
+        let mut new = SmtpInfo::default();
+        new.server = server.into();
+        SmtpTransportBuilder { info: new }
+    }
+}
+
+/// Contains client configuration
+#[allow(missing_debug_implementations)]
+#[derive(Clone)]
+pub struct SmtpTransportBuilder {
+    info: SmtpInfo,
+}
+
+/// Builder for the SMTP `SmtpTransport`
+impl SmtpTransportBuilder {
+    /// Set the name used during EHLO
+    pub fn hello_name(mut self, name: ClientId) -> Self {
+        self.info.hello_name = name;
+        self
+    }
+
+    /// Set the authentication mechanism to use
+    pub fn credentials(mut self, credentials: Credentials) -> Self {
+        self.info.credentials = Some(credentials);
+        self
+    }
+
+    /// Set the authentication mechanism to use
+    pub fn authentication(mut self, mechanisms: Vec<Mechanism>) -> Self {
+        self.info.authentication = mechanisms;
+        self
+    }
+
+    /// Set the timeout duration
+    pub fn timeout(mut self, timeout: Option<Duration>) -> Self {
+        self.info.timeout = timeout;
+        self
+    }
+
+    /// Set the port to use
+    pub fn port(mut self, port: u16) -> Self {
+        self.info.port = port;
+        self
+    }
+
+    /// Set the TLS settings to use
+    #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+    pub fn tls(mut self, tls: Tls) -> Self {
+        self.info.tls = tls;
+        self
+    }
+
+    /// Build the client
+    fn build_client(self) -> SmtpClient {
+        SmtpClient { info: self.info }
+    }
+
+    /// Build the transport with custom pool settings
+    #[cfg(feature = "r2d2")]
+    pub fn build_with_pool(self, pool: Builder<SmtpClient>) -> SmtpTransport {
+        let pool = pool.build_unchecked(self.build_client());
+        SmtpTransport { inner: pool }
+    }
+
+    /// Build the transport (with default pool if enabled)
+    pub fn build(self) -> SmtpTransport {
+        let client = self.build_client();
+        SmtpTransport {
+            #[cfg(feature = "r2d2")]
+            inner: Pool::builder().max_size(5).build_unchecked(client),
+            #[cfg(not(feature = "r2d2"))]
+            inner: client,
+        }
+    }
+}
+
+/// Build client
+#[derive(Clone)]
+pub struct SmtpClient {
+    info: SmtpInfo,
+}
+
+impl SmtpClient {
+    /// Creates a new connection directly usable to send emails
+    ///
+    /// Handles encryption and authentication
+    pub fn connection(&self) -> Result<SmtpConnection, Error> {
+        let mut conn = SmtpConnection::connect::<(&str, u16)>(
+            (self.info.server.as_ref(), self.info.port),
+            self.info.timeout,
+            &self.info.hello_name,
+            #[allow(clippy::match_single_binding)]
+            match self.info.tls {
+                #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+                Tls::Wrapper(ref tls_parameters) => Some(tls_parameters),
+                _ => None,
+            },
+        )?;
+
+        #[allow(clippy::match_single_binding)]
+        match self.info.tls {
+            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+            Tls::Opportunistic(ref tls_parameters) => {
+                if conn.can_starttls() {
+                    conn.starttls(tls_parameters, &self.info.hello_name)?;
+                }
+            }
+            #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
+            Tls::Required(ref tls_parameters) => {
+                conn.starttls(tls_parameters, &self.info.hello_name)?;
+            }
+            _ => (),
+        }
+
+        match &self.info.credentials {
+            Some(credentials) => {
+                conn.auth(self.info.authentication.as_slice(), &credentials)?;
+            }
+            None => (),
+        }
+
+        Ok(conn)
+    }
+}