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 final String USERNAME = "kodejava";
    public static final String PASSWORD = "**********";

    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", ReadEmail.USERNAME);
        props.put("mail.store.protocol", "pop3");

        // 2. Creates a javax.mail.Authenticator object.
        Authenticator auth = new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(ReadEmail.USERNAME, ReadEmail.PASSWORD);
            }
        };

        // 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", ReadEmail.USERNAME, ReadEmail.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();
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>

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

The code snippet below show you how to create a simple Java 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<String> mailSmtpHostComboBox = new JComboBox<>();
    private JTextField usernameField = new JTextField();
    private JPasswordField passwordField = new JPasswordField();
    private JTextArea contentTextArea = new JTextArea();

    private SendEmailClient() {
        InitializeUI();
    }

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

    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(mailSmtpHostComboBox);
        mailSmtpHostComboBox.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);
    }

    private class SendEmailActionListener implements ActionListener {
        SendEmailActionListener() {
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            Properties props = new Properties();
            props.put("mail.smtp.host", mailSmtpHostComboBox.getSelectedItem());
            props.put("mail.transport.protocol", "smtp");
            props.put("mail.smtp.starttls.enable", "true");
            props.put("mail.smtp.auth", "true");
            props.put("mail.smtp.port", "465");
            props.put("mail.smtp.socketFactory.port", "465");
            props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");

            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();
            }
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>

What are the system properties used for sending email?

Here are a list of system properties that can be use to send an e-mail using the JavaMail API.

Property Default Value Description
mail.host Define the host name of the mail server.
mail.smtp.host Define the host name of the SMTP server; this will overrides the mail.host for SMTP connections only.
mail._protocol_.host Define the host name of the specified protocol (POP, IMAP); this will overrides the mail.host.
mail.user Define the default username sent to all mail servers.
mail._protocol_.user Define the default username for the specified protocol; this will overrides the mail.user for the specified protocol.
mail.smtp.port 25 Define the SMTP port on which the SMTP server is listening.
mail._protocol_.port Default port for the corresponding protocol Define the port on which the servers for the specified protocol is listening.
mail.smtp.starttls.enable Upgrade the regular SMTP connection on the usual port to an encrypted (TLS or SSL) connection.
mail.smtp.connectiontimeout Infinite Define the number of milliseconds to wait for a connection timeout.
mail.debug false Define parameter for disabling or enabling information debugging.
mail.from Define the e-mail address to use in the From header.
mail.mime.charset file.encoding Define the default character set used to send messages.
mail.alternates Define other email address for the current that will not to be included when replying to a message.
mail._protocol_.class Define the fully package qualified class name of the provider for the specified protocol.
mail.transport.protocol First transport provider in the configuration file Define default protocol with which to send messages.
mail.transport.protocol.address-type Define the message transport protocol such as SMTP for the specified address type, for example mail.transport.protocol.rfc822.
mail.replayallcc false Put all recipients in the CC list of the reply message instead of the TO field when replying to all.

How do I send an HTML email?

The following code snippets show you how to send an html e-mail. We begin by defining the e-mail information such as the from address, to address and the subject. The next step it to create a Properties that will be used to create a mail Session object. Having a Session object we can then create a Message using the MimeMessage.

We use the MimeMessage.setContent(Object, String) to set the html content of the email. Do not forget to set the content type to text/html and also supply the character set, in the example we use charset=utf-8.

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 java.util.Properties;

public class SendHTMLEmail {
    public static void main(String[] args) {
        String from = "kodejava@gmail.com";
        String to = "kodejava@gmail.com";
        String subject = "Hello";

        Properties props = new Properties();
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.port", "587");
        Session session = Session.getDefaultInstance(props);

        try {
            InternetAddress fromAddress = new InternetAddress(from);
            InternetAddress toAddress = new InternetAddress(to);

            Message message = new MimeMessage(session);
            message.setFrom(fromAddress);
            message.setRecipient(Message.RecipientType.TO, toAddress);
            message.setSubject(subject);

            String sb = "<head>" +
                "<style type=\"text/css\">" +
                "  .red { color: #f00; }" +
                "</style>" +
                "</head>" +
                "<h1 class=\"red\">" + message.getSubject() + "</h1>" +
                "<p>" +
                "Lorem ipsum dolor sit amet, <em>consectetur</em> adipisicing elit, " +
                "sed do eiusmod tempor incididunt ut labore et dolore magna <strong>" +
                "aliqua</strong>.</p>";
            message.setContent(sb, "text/html; charset=utf-8");
            message.saveChanges();

            // Send the message to the recipient. You also need to specify the username 
            // and password to authenticate to the mail server.
            Transport.send(message, "kodejava", "********");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>

How do I send email using Gmail via TLS?

The following example show you how to send email using Gmail SMTP via TLS connection. The username and password is use to authenticate you against the Gmail.

The configuration / properties used for connection to the Gmail SMTP is defined in the createConfiguration() method. The properties include information such as the SMTP host address, port number, etc.

To send email using Gmail via SSL see the following code snippet How do I send email using Gmail via SSL?.

Let’s see the code snippet below:

package org.kodejava.example.mail;

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Date;
import java.util.Properties;

public class GmailSendEmailTLS {
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "********";

    public static void main(String[] args) throws Exception {
        // Email information such as from, to, subject and contents.
        String mailFrom = "kodejava@gmail.com";
        String mailTo = "kodejava@gmail.com";
        String mailSubject = "TLS - Gmail Send Email Demo";
        String mailText = "TLS - Gmail Send Email Demo";

        GmailSendEmailTLS gmail = new GmailSendEmailTLS();
        gmail.sendMail(mailFrom, mailTo, mailSubject, mailText);
    }

    private void sendMail(String mailFrom, String mailTo, String mailSubject,
                          String mailText) throws Exception {

        Properties config = createConfiguration();

        // Creates a mail session. We need to supply username and
        // password for Gmail authentication.
        Session session = Session.getInstance(config, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                    GmailSendEmailTLS.USERNAME,
                    GmailSendEmailTLS.PASSWORD
                );
            }
        });

        // Creates email message
        Message message = new MimeMessage(session);
        message.setSentDate(new Date());
        message.setFrom(new InternetAddress(mailFrom));
        message.setRecipient(Message.RecipientType.TO,
            new InternetAddress(mailTo));
        message.setSubject(mailSubject);
        message.setText(mailText);

        // Send a message
        Transport.send(message, GmailSendEmailTLS.USERNAME, GmailSendEmailTLS.PASSWORD);
    }

    private Properties createConfiguration() {
        return new Properties() {{
            put("mail.smtp.auth", "true");
            put("mail.smtp.host", "smtp.gmail.com");
            put("mail.smtp.port", "587");
            put("mail.smtp.starttls.enable", "true");
        }};
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>

How do I send email using Gmail via SSL?

In another example you’ve seen how to send email using Gmail SMTP via TLS. See the following example How do I send email using Gmail via TLS?.

In this example you will use the SSL connection to connect to Gmail SMTP server. The difference with is in the properties / configuration that we use to create the mail session object.

package org.kodejava.example.mail;

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Date;
import java.util.Properties;

public class GmailSendEmailSSL {
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "********";

    public static void main(String[] args) throws Exception {
        // Email information such as from, to, subject and contents.
        String mailFrom = "kodejava@gmail.com";
        String mailTo = "kodejava@gmail.com";
        String mailSubject = "SSL - Gmail Send Email Demo";
        String mailText = "SSL - Gmail Send Email Demo";

        GmailSendEmailSSL gmail = new GmailSendEmailSSL();
        gmail.sendMail(mailFrom, mailTo, mailSubject, mailText);
    }

    private void sendMail(String mailFrom, String mailTo, String mailSubject,
                          String mailText) throws Exception {

        Properties config = createConfiguration();

        // Creates a mail session. We need to supply username and
        // password for Gmail authentication.
        Session session = Session.getInstance(config, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                    GmailSendEmailSSL.USERNAME,
                    GmailSendEmailSSL.PASSWORD
                );
            }
        });

        // Creates email message
        Message message = new MimeMessage(session);
        message.setSentDate(new Date());
        message.setFrom(new InternetAddress(mailFrom));
        message.setRecipient(Message.RecipientType.TO, new InternetAddress(mailTo));
        message.setSubject(mailSubject);
        message.setText(mailText);

        // Send a message
        Transport.send(message, GmailSendEmailSSL.USERNAME, GmailSendEmailSSL.PASSWORD);
    }

    private Properties createConfiguration() {
        return new Properties() {{
            put("mail.smtp.host", "smtp.gmail.com");
            put("mail.smtp.auth", "true");
            put("mail.smtp.port", "465");
            put("mail.smtp.socketFactory.port", "465");
            put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
        }};
    }
}

There is a chance that you can get an error that tell you cannot connect to the smtp.gmail.com port 465. If this is the case please check your connection to the server using telnet command. The command is telnet smtp.gmail.com 465, and see if there is a reply.

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>

How do I debug application that uses JavaMail APIs?

To ask Java mail to print out a debug message when you run a Java mail program you can add the mail.debug and set the value to true into the properties use to create the session object.

The other way is to set the debug setting of the session using the session.setDebug() method and pass true as the parameter. This will also turn on the debug message in your Java mail program.

package org.kodejava.example.mail;

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Date;
import java.util.Properties;

public class MailDebugDemo {
    public static void main(String[] args) {
        MailDebugDemo.sendMail("kodejava@gmail.com", "kodejava@gmail.com",
            "Debug Demo", "Mail Debug Demo");
    }

    private static void sendMail(String mailFrom, String mailTo, String mailSubject,
                                 String mailText) {
        Properties props = new Properties() {{
            put("mail.smtp.auth", "true");
            put("mail.smtp.host", "smtp.gmail.com");
            put("mail.smtp.port", "587");
            put("mail.smtp.starttls.enable", "true");
            put("mail.debug", "true");
        }};

        // Creates a mail session. We need to supply username and
        // password for GMail authentication.
        Session session = Session.getInstance(props, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication("kodejava", "********");
            }
        });

        try {
            // Creates email message
            Message message = new MimeMessage(session);
            message.setSentDate(new Date());
            message.setFrom(new InternetAddress(mailFrom));
            message.setRecipient(Message.RecipientType.TO,
                new InternetAddress(mailTo));
            message.setSubject(mailSubject);
            message.setText(mailText);

            // Send a message
            Transport.send(message, "kodejava", "********");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}

Here is an example of debug information produce by the JavaMail API when sending an email using Gmail SMTP server.

DEBUG: JavaMail version 1.5.6
DEBUG: successfully loaded resource: /META-INF/javamail.default.providers
DEBUG: Tables of loaded providers
DEBUG: Providers Listed By Class Name: {com.sun.mail.smtp.SMTPSSLTransport=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Oracle], com.sun.mail.smtp.SMTPTransport=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle], com.sun.mail.imap.IMAPSSLStore=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Oracle], com.sun.mail.pop3.POP3SSLStore=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Oracle], com.sun.mail.imap.IMAPStore=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Oracle], com.sun.mail.pop3.POP3Store=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Oracle]}
DEBUG: Providers Listed By Protocol: {imaps=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Oracle], imap=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Oracle], smtps=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Oracle], pop3=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Oracle], pop3s=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Oracle], smtp=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle]}
DEBUG: successfully loaded resource: /META-INF/javamail.default.address.map
DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle]
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: trying to connect to host "smtp.gmail.com", port 587, isSSL false
220 smtp.gmail.com ESMTP e64sm51975202pfl.49 - gsmtp
DEBUG SMTP: connected to host "smtp.gmail.com", port: 587

EHLO pluto
250-smtp.gmail.com at your service, [180.252.60.172]
250-SIZE 35882577
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
DEBUG SMTP: Found extension "SIZE", arg "35882577"
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "STARTTLS", arg ""
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "CHUNKING", arg ""
DEBUG SMTP: Found extension "SMTPUTF8", arg ""
STARTTLS
220 2.0.0 Ready to start TLS
EHLO pluto
250-smtp.gmail.com at your service, [180.252.60.172]
250-SIZE 35882577
250-8BITMIME
250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
DEBUG SMTP: Found extension "SIZE", arg "35882577"
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "AUTH", arg "LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH"
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "CHUNKING", arg ""
DEBUG SMTP: Found extension "SMTPUTF8", arg ""
DEBUG SMTP: Attempt to authenticate using mechanisms: LOGIN PLAIN DIGEST-MD5 NTLM 
DEBUG SMTP: AUTH LOGIN command trace suppressed
DEBUG SMTP: AUTH LOGIN succeeded
DEBUG SMTP: use8bit false
MAIL FROM:
250 2.1.0 OK e64sm51975202pfl.49 - gsmtp
RCPT TO:
250 2.1.5 OK e64sm51975202pfl.49 - gsmtp
DEBUG SMTP: Verified Addresses
DEBUG SMTP:   kodejava@gmail.com
DATA
354  Go ahead e64sm51975202pfl.49 - gsmtp
Date: Mon, 5 Jun 2017 12:12:54 +0800 (WITA)
From: kodejava@gmail.com
To: kodejava@gmail.com
Message-ID: <1368884364.0.1496635974662@pluto>
Subject: Debug Demo
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

Mail Debug Demo
.
250 2.0.0 OK 1496635979 e64sm51975202pfl.49 - gsmtp
QUIT
221 2.0.0 closing connection e64sm51975202pfl.49 - gsmtp

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>

How do I validate email address using Java Mail API?

This code snippet shows you how to validate an email address using the javax.mail.internet.InternetAddress class. The validate() method throws a javax.mail.internet.AddressException when the email address passed to the constructor is not a valid email address.

Here is the complete code snippet:

package org.kodejava.example.mail;

import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;

public class ValidateEmail {
    public static void main(String[] args) {
        ValidateEmail demo = new ValidateEmail();

        String email = "kodejava@gmail.com";
        boolean isValid = demo.validateEmail(email);
        demo.printStatus(email, isValid);

        email = "kodejava.gmail";
        isValid = demo.validateEmail(email);
        demo.printStatus(email, isValid);
    }

    private boolean validateEmail(String email) {
        boolean isValid = false;
        try {
            // Create InternetAddress object and validated the supplied
            // address which is this case is an email address.
            InternetAddress internetAddress = new InternetAddress(email);
            internetAddress.validate();
            isValid = true;
        } catch (AddressException e) {
            e.printStackTrace();
        }
        return isValid;
    }

    private void printStatus(String email, boolean valid) {
        System.out.println(email + " is " + (valid ? "a" : "not a") +
                " valid email address");
    }
}

When running the program you will get the following message printed on the screen. For simplicity I’ve remove the complete error stack trace.

kodejava@gmail.com is a valid email address
kodejava.gmail is not a valid email address

Maven Dependency

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>

How do I validate email address using regular expression?

In this examples we use the String‘s class matches() methods to match a string to be a valid email address based on the given regex.

This examples also demonstrate the power of regular expression to validate an email address. Using regular expression makes it easier to validate data such as email. After the code you’ll see the meaning of the regular expression used in the code below.

package org.kodejava.example.lang;

public class EmailAddressValidation {
    private static final String EMAIL_REGEX =
        "^[\\w-_\\.+]*[\\w-_\\.]\\@([\\w]+\\.)+[\\w]+[\\w]$";

    public static void main(String[] args) {
        EmailAddressValidation validator = new EmailAddressValidation();

        System.out.println("isValid = "
            + validator.isValidEmailAddress("user@domain.com"));
        System.out.println("isValid = "
            + validator.isValidEmailAddress("user.name@domain.com"));
        System.out.println("isValid = "
            + validator.isValidEmailAddress("user.name@domain.com.sg"));
        System.out.println("isValid = "
            + validator.isValidEmailAddress("user.domain.com.sg"));
    }

    /**
     * Validates email address against email regular expression.
     *
     * @param email an email address to check
     * @return true if email address is valid otherwise return false.
     */
    private boolean isValidEmailAddress(String email) {
        return email.matches(EMAIL_REGEX);
    }
}

The first ^[\w-_\.+]. The ^ symbols means check the first character. This the regex processor that the email address should start with a word character formed of alphanumeric value (a-z 0-9) or it can also be an hyphen, underscore, dot or a plus symbol.

The second part, *[\w-_\.]. The * symbol means match the preceding zero or more times. As the first part, this tell the regex processor to check for another zero or more characters, and it can also contains hyphen, underscore and a dot.

The third part, \@([\w]+\.)+. This check that email address should contains the @ symbol followed by one or more word separated by the dot symbol.

The last part is, [\w]+[\w]$, this check that after the last period there should be another word for the domain suffix such as the co.uk or co.id. And the $ ask that the email address should ends by a word character.

How do I send an email with attachment?

In this example we create a small program to send email with a file attachment. To send message with attachment we need to create an email with javax.mail.Multipart object which basically will contains the email text message and then add a file to the second block, which both of them is an object of javax.mail.internet.MimeBodyPart. In this example we also use the javax.activation.FileDataSource.

package org.kodejava.example.mail;

import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import java.util.Date;
import java.util.Properties;

public class SendEmailWithAttachment {
    public static void main(String[] args) {
        SendEmailWithAttachment demo = new SendEmailWithAttachment();
        demo.sendEmail();
    }

    public void sendEmail() {
        // Defines the E-Mail information.
        String from = "kodejava@gmail.com";
        String to = "kodejava@gmail.com";
        String subject = "Important Message";
        String bodyText = "This is a important message with attachment.";

        // The attachment file name.
        String attachmentName = "D:/Temp/hello.txt";

        // Creates a Session with the following properties.
        Properties props = new Properties();
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.port", "587");
        Session session = Session.getDefaultInstance(props);

        try {
            InternetAddress fromAddress = new InternetAddress(from);
            InternetAddress toAddress = new InternetAddress(to);

            // Create an Internet mail msg.
            MimeMessage msg = new MimeMessage(session);
            msg.setFrom(fromAddress);
            msg.setRecipient(Message.RecipientType.TO, toAddress);
            msg.setSubject(subject);
            msg.setSentDate(new Date());

            // Set the email msg text.
            MimeBodyPart messagePart = new MimeBodyPart();
            messagePart.setText(bodyText);

            // Set the email attachment file
            FileDataSource fileDataSource = new FileDataSource(attachmentName);

            MimeBodyPart attachmentPart = new MimeBodyPart();
            attachmentPart.setDataHandler(new DataHandler(fileDataSource));
            attachmentPart.setFileName(fileDataSource.getName());

            // Create Multipart E-Mail.
            Multipart multipart = new MimeMultipart();
            multipart.addBodyPart(messagePart);
            multipart.addBodyPart(attachmentPart);

            msg.setContent(multipart);

            // Send the msg. Don't forget to set the username and password
            // to authenticate to the mail server.
            Transport.send(msg, "kodejava", "********");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<!-- http://repo1.maven.org/maven2/javax/mail/javax.mail-api/1.5.6/javax.mail-api-1.5.6.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>javax.mail-api</artifactId>
    <version>1.5.6</version>
</dependency>
<!-- http://repo1.maven.org/maven2/javax/mail/mail/1.4.7/mail-1.4.7.jar -->
<dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
    <version>1.4.7</version>
</dependency>