daaki-smtp

A Rust SMTP/LMTP client built with tokio & rustls.

Highlights

• SMTP and LMTP — support for RFC 5321 and RFC 2033.
• Pipelining — batches commands automatically when the server advertises it.
• CHUNKING/BINARYMIME — send large or binary messages via BDAT without dot-stuffing.
• Async with explicit timeouts — built on tokio. Every operation takes a Duration.
• TLS by default — rustls-based TLS with implicit TLS (port 465) and STARTTLS.
• Typed API — validated newtypes (ReversePath, ForwardPath, Domain, Mailbox) and typed results (SendResult, LmtpSendResult) catch errors at construction time.
• Zero unsafe code — enforced by #![deny(unsafe_code)] crate-wide.
• Optional serde — enable the serde feature for Serialize/Deserialize on all public types.

Quick Start

[dependencies]
daaki-smtp = "0.2"

Connect, authenticate, and send a message:

use daaki_smtp::{SmtpConnection, TlsMode, ReversePath, ForwardPath};
use std::time::Duration;

#[tokio::main]
async fn main() -> daaki_smtp::Result<()> {
    let timeout = Duration::from_secs(30);

    let conn = SmtpConnection::connect(
        "smtp.example.com", 465, TlsMode::Implicit, timeout,
    ).await?;
    conn.auth_plain("user@example.com", "password", timeout).await?;

    let message = b"From: user@example.com\r\n\
                    To: recipient@example.com\r\n\
                    Subject: Hello\r\n\
                    \r\n\
                    Hello, world!\r\n";

    let from = ReversePath::new("user@example.com")?;
    let to = vec![ForwardPath::new("recipient@example.com")?];
    conn.send(&from, &to, message, timeout).await?;
    conn.quit(timeout).await?;
    Ok(())
}

LMTP

Connect to an LMTP server for local delivery. Returns per-recipient results:

# use daaki_smtp::{SmtpConnection, TlsMode, ReversePath, ForwardPath};
# use std::time::Duration;
# async fn example() -> daaki_smtp::Result<()> {
let timeout = Duration::from_secs(30);

let conn = SmtpConnection::connect_lmtp(
    "localhost", 24, TlsMode::None, timeout,
).await?;

let from = ReversePath::new("user@example.com")?;
let to = vec![ForwardPath::new("local@example.com")?];
let result = conn.send_lmtp(&from, &to, b"Subject: Hi\r\n\r\nHello\r\n", None, timeout).await?;

for r in &result.results {
    println!("{}: {}", r.recipient, r.response.text());
}
# Ok(())
# }

Supported Extensions

Compatibility note: some servers advertise a legacy, non-standard SASL-IR EHLO keyword. daaki-smtp preserves it for introspection, but RFC 4954 Section 4 already allows SMTP AUTH initial responses without a separate standard extension.

License

The contents of this package are licensed under the terms of the MIT license.