How do I receive mail using POP3?

In this example you will learn how to receive email using POP3. We are going to connect to Gmail server and read the messages in the INBOX folder. There are some steps that you need to do to download this email. Here are the steps:

  1. Setup properties for the mail session.
  2. Creates a javax.mail.Authenticator object.
  3. Creating mail session.
  4. Get the POP3 store provider and connect to the store.
  5. Get folder and open the INBOX folder in the store.
  6. Retrieve the messages from the folder.
  7. Close folder and close store.

These steps can be written as the following code snippet:

package org.kodejava.example.mail;

import javax.mail.*;
import java.util.Properties;

public class ReadEmail {
    public static void main(String[] args) throws Exception {
        //
        // 1. Setup properties for the mail session.
        //
        Properties props = new Properties();
        props.put("mail.pop3.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
        props.put("mail.pop3.socketFactory.fallback", "false");
        props.put("mail.pop3.socketFactory.port", "995");
        props.put("mail.pop3.port", "995");
        props.put("mail.pop3.host", "pop.gmail.com");
        props.put("mail.pop3.user", "kodejava");
        props.put("mail.store.protocol", "pop3");

        //
        // 2. Creates a javax.mail.Authenticator object.
        //
        Authenticator auth = null;

        //
        // 3. Creating mail session.
        //
        Session session = Session.getDefaultInstance(props, auth);

        //
        // 4. Get the POP3 store provider and connect to the store.
        //
        Store store = session.getStore("pop3");
        store.connect("pop.gmail.com", "kodejava", "password");

        //
        // 5. Get folder and open the INBOX folder in the store.
        //
        Folder inbox = store.getFolder("INBOX");
        inbox.open(Folder.READ_ONLY);

        //
        // 6. Retrieve the messages from the folder.
        //
        Message[] messages = inbox.getMessages();
        for (Message message : messages) {
            message.writeTo(System.out);
        }

        //
        // 7. Close folder and close store.
        //
        inbox.close(false);
        store.close();
    }
}

 

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 {
    JTextField fromField = new JTextField();
    JTextField toField = new JTextField();
    JTextField subjectField = new JTextField();
    JComboBox mailServer = new JComboBox();
    JTextField usernameField = new JTextField();
    JPasswordField passwordField = new JPasswordField();
    JTextArea contentTextArea = new JTextArea();

    public SendEmailClient() {
        InitializeUI();
    }

    private void InitializeUI() {
        setTitle("Send E-mail Client");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        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(fromField);

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

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

        headerPanel.add(new JLabel("STMP Server:"));
        headerPanel.add(mailServer);
        mailServer.addItem("smtp.gmail.com");

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

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

        //
        // 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);
    }

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

    class SendEmailActionListener implements ActionListener {
        SendEmailActionListener() {
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            Properties props = new Properties();
            props.put("mail.smtp.host", 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.setFrom(fromAddress);
                message.setRecipient(Message.RecipientType.TO, toAddress);
                message.setSubject(subjectField.getText());
                message.setText(contentTextArea.getText());

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