lettre

A mailer library for Rust

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NOTE: this readme refers to the 0.10 version of lettre, which is in release candidate state. Use the v0.9.x branch for the previous stable release.

0.10 is already widely used and is already thought to be more reliable than 0.9, so it should generally be used for new projects.

We'd love to hear your feedback about 0.10 design and APIs before final release! Start a discussion in the repository, whether for feedback or if you need help or advice using or upgrading lettre 0.10.

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Features

Lettre provides the following features:

• Multiple transport methods
• Unicode support (for email content and addresses)
• Secure delivery with SMTP using encryption and authentication
• Easy email builders
• Async support

Lettre does not provide (for now):

• Email parsing

Example

This library requires Rust 1.52.1 or newer. To use this library, add the following to your Cargo.toml:

[dependencies]
lettre = "0.10.0-rc.4"

use lettre::transport::smtp::authentication::Credentials;
use lettre::{Message, SmtpTransport, Transport};

let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse().unwrap())
    .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
    .to("Hei <hei@domain.tld>".parse().unwrap())
    .subject("Happy new year")
    .body(String::from("Be happy!"))
    .unwrap();

let creds = Credentials::new("smtp_username".to_string(), "smtp_password".to_string());

// Open a remote connection to gmail
let mailer = SmtpTransport::relay("smtp.gmail.com")
    .unwrap()
    .credentials(creds)
    .build();

// Send the email
match mailer.send(&email) {
    Ok(_) => println!("Email sent successfully!"),
    Err(e) => panic!("Could not send email: {:?}", e),
}

Testing

The lettre tests require an open mail server listening locally on port 2525 and the sendmail command. If you have python installed such a server can be launched with python -m smtpd -n -c DebuggingServer localhost:2525

Alternatively only unit tests can be run by doing cargo test --lib.

Troubleshooting

These are general steps to be followed when troubleshooting SMTP related issues.

• Ensure basic connectivity, ensure requisite ports are open and daemons are listening.
• Confirm that your service provider allows traffic on the ports being used for mail transfer.
• Check SMTP relay authentication and configuration.
• Validate your DNS records. (DMARC, SPF, DKIM, MX)
• Verify your SSL/TLS certificates are setup properly.
• Investigate if filtering, formatting, or filesize limits are causing messages to be lost, delayed, or blocked by relays or remote hosts.

Code of conduct

Anyone who interacts with Lettre in any space, including but not limited to this GitHub repository, must follow our code of conduct.

License

This program is distributed under the terms of the MIT license.

The builder comes from emailmessage-rs by Kayo, under MIT license.

See LICENSE for details.