How do I create a simple mail client program in Swing?

The code snippet below show you how to create a simple swing application that can be used to send an e-mail. The program allows user to supply the from email address, to email address, the subject and the message of the email. User need to select the available smtp server to connect to and provide the username and password for authentication the the mail server.

Here is the user interface of this simple email client:

Simple E-mail Client

Simple E-mail Client

The main routine for sending the email is in the SendEmailActionListener class, which is an implementation of an ActionListener interface that will handle the emailing process when the Send E-mail button is pressed.

package org.kodejava.example.mail;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Properties;

public class SendEmailClient extends JFrame {
    private JTextField fromField = new JTextField();
    private JTextField toField = new JTextField();
    private JTextField subjectField = new JTextField();
    private JComboBox mailServer = new JComboBox();
    private JTextField usernameField = new JTextField();
    private JPasswordField passwordField = new JPasswordField();
    private JTextArea contentTextArea = new JTextArea();

    private SendEmailClient() {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                SendEmailClient client = new SendEmailClient();

    private void InitializeUI() {
        setTitle("Send E-mail Client");
        setSize(new Dimension(400, 280));

        getContentPane().setLayout(new BorderLayout());

        // Header Panel
        JPanel headerPanel = new JPanel();
        headerPanel.setLayout(new GridLayout(6, 2));
        headerPanel.add(new JLabel("From:"));

        headerPanel.add(new JLabel("To:"));

        headerPanel.add(new JLabel("Subject:"));

        headerPanel.add(new JLabel("STMP Server:"));

        headerPanel.add(new JLabel("Username:"));

        headerPanel.add(new JLabel("Password:"));

        // Body Panel
        JPanel bodyPanel = new JPanel();
        bodyPanel.setLayout(new BorderLayout());
        bodyPanel.add(new JLabel("Message:"), BorderLayout.NORTH);
        bodyPanel.add(contentTextArea, BorderLayout.CENTER);

        JPanel footerPanel = new JPanel();
        footerPanel.setLayout(new BorderLayout());
        JButton sendMailButton = new JButton("Send E-mail");
        sendMailButton.addActionListener(new SendEmailActionListener());

        footerPanel.add(sendMailButton, BorderLayout.SOUTH);

        getContentPane().add(headerPanel, BorderLayout.NORTH);
        getContentPane().add(bodyPanel, BorderLayout.CENTER);
        getContentPane().add(footerPanel, BorderLayout.SOUTH);

    private class SendEmailActionListener implements ActionListener {
        SendEmailActionListener() {

        public void actionPerformed(ActionEvent e) {
            Properties props = new Properties();
            props.put("", mailServer.getSelectedItem());
            props.put("mail.transport.protocol", "smtp");
            props.put("mail.smtp.starttls.enable", "true");

            Session session = Session.getDefaultInstance(props);

            try {
                InternetAddress fromAddress = new InternetAddress(fromField.getText());
                InternetAddress toAddress = new InternetAddress(toField.getText());

                Message message = new MimeMessage(session);
                message.setRecipient(Message.RecipientType.TO, toAddress);

                Transport.send(message, usernameField.getText(),
                        new String(passwordField.getPassword()));
            } catch (MessagingException ex) {