JavaMail: Sending Email in Java

What is JavaMail?

JavaMail (jakarta.mail / javax.mail) is the standard Java API to send and receive email using SMTP, POP3 and IMAP. With it, your application can send welcome emails, password resets, invoices and notifications.

Minimum Dependencies

• jakarta.mail (or javax.mail) - the API.
• jakarta.activation - used for data handlers.

Sending a Text Email

import jakarta.mail.*;
import jakarta.mail.internet.*;
import java.util.Properties;

public class SendMail {
    public static void main(String[] args) throws Exception {
        String host = "smtp.gmail.com";
        String from = "you@gmail.com";
        String password = "app-password";
        String to = "friend@example.com";

        Properties props = new Properties();
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");

        Session session = Session.getInstance(props,
            new Authenticator() {
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(from, password);
                }
            });

        Message message = new MimeMessage(session);
        message.setFrom(new InternetAddress(from));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
        message.setSubject("Hello from JavaMail");
        message.setText("This email was sent from a Java program.");

        Transport.send(message);
        System.out.println("Email sent.");
    }
}

HTML Emails

message.setContent("<h1>Welcome!</h1><p>Thanks for signing up.</p>", "text/html; charset=utf-8");

Key Points

• SMTP credentials are secrets - keep them in environment variables or a config server.
• Gmail and most providers expect an app password, not your account password, for SMTP.
• Use TLS/STARTTLS on port 587 for sending through providers.