Rust

Open a Persistent SMTP Connection

Demonstrates the Chilkat MailMan.OpenSmtpConnection method, which explicitly opens a connection to the SMTP server and authenticates if a username and password, OAuth2 token, or other applicable settings have been provided. This example opens the connection, notes where sending would occur, and closes it.

Background: By default, sending a single email opens a connection, sends, and closes it. When sending many messages, that per-message overhead adds up. Explicitly calling OpenSmtpConnection once, sending in a loop, then CloseSmtpConnection keeps a single authenticated session open for the whole batch — substantially faster and gentler on the server than reconnecting each time.

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Rust


// Demonstrates the MailMan.OpenSmtpConnection method, which explicitly opens a connection
// to the SMTP server and authenticates if credentials (or an OAuth2 token) have been
// provided.

let mailman = chilkat::MailMan::new();

// Configure the SMTP server connection.
mailman.set_smtp_host("smtp.example.com");
mailman.set_smtp_port(465);
mailman.set_smtp_ssl(true);
mailman.set_smtp_username("user@example.com");
mailman.set_smtp_password("myPassword");

// Explicitly open (and authenticate) the SMTP connection.

if mailman.open_smtp_connection().is_err() {
    println!("{}", mailman.last_error_text());
    return;
}

println!("SMTP connection opened.");

// ... send one or more emails here ...

// Close the connection when done.
if mailman.close_smtp_connection().is_err() {
    println!("{}", mailman.last_error_text());
    return;
}