Module lettre::smtp [−] [src]

The SMTP transport sends emails using the SMTP protocol.

This SMTP client follows RFC 5321, and is designed to efficiently send emails from an application to a relay email server, as it relies as much as possible on the relay server for sanity and RFC compliance checks.

It implements the following extensions:

8BITMIME (RFC 6152)
AUTH (RFC 4954) with PLAIN, LOGIN and CRAM-MD5 mechanisms
STARTTLS (RFC 2487)
SMTPUTF8 (RFC 6531)

Simple example

This is the most basic example of usage:

use lettre::{SimpleSendableEmail, EmailTransport, EmailAddress, SmtpTransport};

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

// Open a local connection on port 25
let mut mailer =
SmtpTransport::builder_unencrypted_localhost().unwrap().build();
// Send the email
let result = mailer.send(&email);

assert!(result.is_ok());

Complete example

use lettre::smtp::authentication::{Credentials, Mechanism};
use lettre::smtp::SUBMISSION_PORT;
use lettre::{SimpleSendableEmail, EmailTransport, EmailAddress, SmtpTransport};
use lettre::smtp::extension::ClientId;
use lettre::smtp::ConnectionReuseParameters;


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

// Connect to a remote server on a custom port
let mut mailer = SmtpTransport::simple_builder("server.tld".to_string()).unwrap()
    // Set the name sent during EHLO/HELO, default is `localhost`
    .hello_name(ClientId::Domain("my.hostname.tld".to_string()))
    // Add credentials for authentication
    .credentials(Credentials::new("username".to_string(), "password".to_string()))
    // Enable SMTPUTF8 if the server supports it
    .smtp_utf8(true)
    // Configure expected authentication mechanism
    .authentication_mechanism(Mechanism::Plain)
    // Enable connection reuse
    .connection_reuse(ConnectionReuseParameters::ReuseUnlimited).build();

let result_1 = mailer.send(&email);
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();

Lower level

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

use lettre::EmailAddress;
use lettre::smtp::SMTP_PORT;
use lettre::smtp::client::Client;
use lettre::smtp::client::net::NetworkStream;
use lettre::smtp::extension::ClientId;
use lettre::smtp::commands::*;

let mut email_client: Client<NetworkStream> = Client::new();
let _ = email_client.connect(&("localhost", SMTP_PORT), None);
let _ = email_client.smtp_command(EhloCommand::new(ClientId::new("my_hostname".to_string())));
let _ = email_client.smtp_command(
            MailCommand::new(Some(EmailAddress::new("user@example.com".to_string())), vec![])
        );
let _ = email_client.smtp_command(
            RcptCommand::new(EmailAddress::new("user@example.org".to_string()), vec![])
        );
let _ = email_client.smtp_command(DataCommand);
let _ = email_client.message(Box::new("Test email".as_bytes()));
let _ = email_client.smtp_command(QuitCommand);

Modules

authentication	Provides authentication mechanisms
client	SMTP client
commands	SMTP commands
error	Error and result type for SMTP clients
extension	ESMTP features
response	SMTP response, containing a mandatory return code and an optional text message
util	Utils for string manipulation

Structs

SmtpTransport	Structure that implements the high level SMTP client
SmtpTransportBuilder	Contains client configuration

Enums

ClientSecurity	How to apply TLS to a client connection
ConnectionReuseParameters	Configures connection reuse behavior

Constants

COLON	Colon
CRLF	The line ending for SMTP transactions (carriage return + line feed)
MESSAGE_ENDING	The ending of message content
NUL	NUL unicode character
SMTP_PORT	Default smtp port
SP	The word separator for SMTP transactions
SUBMISSION_PORT	Default submission port