lettre/website/content/sending-messages/smtp.md

+++ date = "2017-05-21T23:46:17+02:00" title = "SMTP transport" toc = true weight = 2

+++

This transport uses the SMTP protocol to send emails over the network (locally or remotely).

It is desinged to be:

• Secured: email are encrypted by default
• Modern: Unicode support for email content and sender/recipient adresses when compatible
• Fast: supports tcp connection reuse

This client is designed to send emails to a relay server, and should not be used to send emails directly to the destination.

The relay server can be the local email server, a specific host or a third-party service.

Simple example

This is the most basic example of usage:

{{< highlight rust >}} use lettre::{SimpleSendableEmail, EmailTransport}; use lettre::smtp::SmtpTransportBuilder; use lettre::smtp::SecurityLevel;

let email = SimpleSendableEmail::new( "user@localhost", vec!["root@localhost"], "message_id", "Hello world" );

// Open a local connection on port 25 let mut mailer = SmtpTransportBuilder::localhost().unwrap().security_level(SecurityLevel::Opportunistic).build(); // Send the email let result = mailer.send(email);

assert!(result.is_ok()); {{< /highlight >}}

Complete example

{{< highlight rust >}} use lettre::smtp::{SecurityLevel, SmtpTransport, SmtpTransportBuilder}; use lettre::smtp::authentication::Mechanism; use lettre::smtp::SUBMISSION_PORT; use lettre::{SimpleSendableEmail, EmailTransport};

let email = SimpleSendableEmail::new( "user@localhost", vec!["root@localhost"], "message_id", "Hello world" );

// Connect to a remote server on a custom port let mut mailer = SmtpTransportBuilder::new(("server.tld", SUBMISSION_PORT)).unwrap() // Set the name sent during EHLO/HELO, default is localhost .hello_name("my.hostname.tld") // Add credentials for authentication .credentials("username", "password") // Specify a TLS security level. You can also specify an SslContext with // .ssl_context(SslContext::Ssl23) .security_level(SecurityLevel::AlwaysEncrypt) // Enable SMTPUTF8 if the server supports it .smtp_utf8(true) // Configure expected authentication mechanism .authentication_mechanism(Mechanism::CramMd5) // Enable connection reuse .connection_reuse(true).build();

let result_1 = mailer.send(email.clone()); assert!(result_1.is_ok());

// The second email will use the same connection let result_2 = mailer.send(email); assert!(result_2.is_ok());

// Explicitly close the SMTP transaction as we enabled connection reuse mailer.close(); {{< /highlight >}}

Lower level

You can also send commands, here is a simple email transaction without error handling:

{{< highlight rust >}} use lettre::smtp::SMTP_PORT; use lettre::smtp::client::Client; use lettre::smtp::client::net::NetworkStream;

let mut email_client: Client = Client::new(); let _ = email_client.connect(&("localhost", SMTP_PORT), None); let _ = email_client.ehlo("my_hostname"); let _ = email_client.mail("user@example.com", None); let _ = email_client.rcpt("user@example.org"); let _ = email_client.data(); let _ = email_client.message("Test email"); let _ = email_client.quit(); {{< /highlight >}}