Sending Email in Rust: lettre and mailparse Libraries for Messages

Sending Email in Rust: Powerful Tools for Working with Mail

Rust is a systems programming language increasingly used for building reliable and high-performance web services. One common task is sending emails. In this article, we will thoroughly examine two key libraries in the Rust ecosystem for working with email: lettre (sending) and mailparse (parsing). You will learn how to configure an SMTP client, send an email with attachments, and process incoming mail.

The lettre Library: Sending Emails via SMTP

lettre is a modern, asynchronous and synchronous library for sending email via SMTP, SMTP-SSL, and STARTTLS. It supports:

• Sending text and HTML emails
• Attachments (images, documents, archives)
• Authentication (LOGIN, PLAIN, XOAUTH2)
• DKIM signing and TLS encryption
• Working with async/await (tokio, async-std)

To get started, add the dependency to your Cargo.toml:

[dependencies]lettre = { version = "0.11", features = ["builder", "smtp-transport", "tokio1-rustls-tls"] }tokio = { version = "1", features = ["full"] }

Basic Example: Sending a Text Email

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

#[tokio::main]async fn main() -> Result<(), Box<dyn std::error::Error>> {    // Build the email    let email = Message::builder()        .from("Sender <sender@example.com>".parse()?)        .to("Recipient <recipient@example.com>".parse()?)        .subject("Hello from Rust!")        .body("This is a test email sent using the lettre library.".to_string())?;

    // SMTP configuration (Gmail, Yandex, Mail.ru, etc.)    let creds = Credentials::new("sender@example.com".to_string(), "your_password".to_string());    let mailer = SmtpTransport::relay("smtp.gmail.com")?        .credentials(creds)        .build();

    // Sending    match mailer.send(&email) {        Ok(_) => println!("Email sent successfully!"),        Err(e) => eprintln!("Error sending: {}", e),    }    Ok(())}

Sending an HTML Email with Attachments

To send an email with HTML markup and a file, use MultiPart:

use lettre::message::{header, MultiPart, SinglePart};use lettre::{Message, SmtpTransport, Transport};use std::fs;

let file_content = fs::read("document.pdf")?;let attachment = SinglePart::builder()    .header(header::ContentType::parse("application/pdf")?)    .header(header::ContentDisposition::attachment("document.pdf"))    .body(file_content);

let html_part = SinglePart::builder()    .header(header::ContentType::TEXT_HTML)    .body(String::from("<h1>Hello!</h1><p>This is an HTML email with an attachment.</p>"));

let email = Message::builder()    .from("sender@example.com".parse()?)    .to("recipient@example.com".parse()?)    .subject("HTML + attachment")    .multipart(        MultiPart::mixed()            .multipart(MultiPart::alternative().singlepart(html_part))            .singlepart(attachment),    )?;

The mailparse Library: Parsing Incoming Emails

mailparse is a lightweight library for parsing email messages in MIME format. It is useful if you are processing mail via IMAP/POP3 or reading .eml files. Key features:

• Extracting headers (From, To, Subject, Date)
• Retrieving the email body (text/HTML)
• Extracting attachments with MIME types
• Decoding Base64 and Quoted-Printable

Example: Reading a .eml File

use mailparse::*;

fn main() {    let eml_content = std::fs::read("email.eml")