created_at2024-01-06 12:52:05.984494
updated_at2024-01-06 13:13:14.258122
descriptionE-mail delivery library with SMTP and DKIM support



mail-send build

mail-send is a Rust library to build, sign and send e-mail messages via SMTP. It includes the following features:

  • Generates e-mail messages conforming to the Internet Message Format standard (RFC 5322).
  • Full MIME support (RFC 2045 - 2049) with automatic selection of the most optimal encoding for each message body part.
  • DomainKeys Identified Mail (DKIM) Signatures (RFC 6376) with ED25519-SHA256, RSA-SHA256 and RSA-SHA1 support.
  • Simple Mail Transfer Protocol (SMTP; RFC 5321) delivery.
  • SMTP Service Extension for Secure SMTP over TLS (RFC 3207).
  • SMTP Service Extension for Authentication (RFC 4954) with automatic mechanism negotiation (from most secure to least secure):
    • CRAM-MD5 (RFC 2195)
    • DIGEST-MD5 (RFC 2831; obsolete but still supported)
    • XOAUTH2 (Google proprietary)
    • LOGIN
    • PLAIN
  • Full async (requires Tokio).

Usage Example

Send a message via an SMTP server that requires authentication:

    // Build a simple multipart message
    let message = MessageBuilder::new()
        .from(("John Doe", ""))
            ("Jane Doe", ""),
            ("James Smith", ""),
        .html_body("<h1>Hello, world!</h1>")
        .text_body("Hello world!");

    // Connect to the SMTP submissions port, upgrade to TLS and
    // authenticate using the provided credentials.
    SmtpClientBuilder::new("", 587)
        .credentials(("john", "p4ssw0rd"))

Sign a message with DKIM and send it via an SMTP relay server:

    // Build a simple text message with a single attachment
    let message = MessageBuilder::new()
        .from(("John Doe", ""))
        .text_body("These pretzels are making me thirsty.")
        .attachment("image/png", "pretzels.png", [1, 2, 3, 4].as_ref());

    // Sign an e-mail message using RSA-SHA256
    let pk_rsa = RsaKey::<Sha256>::from_rsa_pem(TEST_KEY).unwrap();
    let signer = DkimSigner::from_key(pk_rsa)
        .headers(["From", "To", "Subject"])
        .expiration(60 * 60 * 7); // Number of seconds before this signature expires (optional)

    // Connect to an SMTP relay server over TLS.
    // Signs each message with the configured DKIM signer.
    SmtpClientBuilder::new("", 465)
        .send_signed(message, &signer)

More examples of how to build messages are available in the mail-builder crate. Please note that this library does not support parsing e-mail messages as this functionality is provided separately by the mail-parser crate.


To run the testsuite:

 $ cargo test --all-features

or, to run the testsuite with MIRI:

 $ cargo +nightly miri test --all-features


Licensed under either of

at your option.


Copyright (C) 2020-2022, Stalwart Labs Ltd.

Commit count: 75

cargo fmt