Outgoing Mail (SMTP) Server
requires TLS or SSL: smtp.gmail.com (use authentication)
Use Authentication: Yes
Port for TLS/STARTTLS: 587
Port for SSL: 465

package com.mkyong.common;
 
import java.util.Properties;
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;
 
public class SendMailTLS {
 
	public static void main(String[] args) {
		String host = "smtp.gmail.com";
		int port = 587;
		String username = "username";
		String password = "password";
 
		Properties props = new Properties();
		props.put("mail.smtp.auth", "true");
		props.put("mail.smtp.starttls.enable", "true");
 
		Session session = Session.getInstance(props);
 
		try {
 
			Message message = new MimeMessage(session);
			message.setFrom(new InternetAddress("from@no-spam.com"));
			message.setRecipients(Message.RecipientType.TO,
				InternetAddress.parse("to@no-spam.com"));
			message.setSubject("Testing Subject");
			message.setText("Dear Mail Crawler," +
					"\n\n No spam to my email, please!");
 
			Transport transport = session.getTransport("smtp");
			transport.connect(host, port, username, password);
 
			Transport.send(message);
 
			System.out.println("Done");
 
		} catch (MessagingException e) {
			throw new RuntimeException(e);
		}
	}
}

package com.mkyong.common;
 
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
 
public class SendMailSSL {
	public static void main(String[] args) {
		Properties props = new Properties();
		props.put("mail.smtp.host", "smtp.gmail.com");
		props.put("mail.smtp.socketFactory.port", "465");
		props.put("mail.smtp.socketFactory.class",
				"javax.net.ssl.SSLSocketFactory");
		props.put("mail.smtp.auth", "true");
		props.put("mail.smtp.port", "465");
 
		Session session = Session.getDefaultInstance(props,
			new javax.mail.Authenticator() {
				protected PasswordAuthentication getPasswordAuthentication() {
					return new PasswordAuthentication("username","password");
				}
			});
 
		try {
 
			Message message = new MimeMessage(session);
			message.setFrom(new InternetAddress("from@no-spam.com"));
			message.setRecipients(Message.RecipientType.TO,
					InternetAddress.parse("to@no-spam.com"));
			message.setSubject("Testing Subject");
			message.setText("Dear Mail Crawler," +
					"\n\n No spam to my email, please!");
 
			Transport.send(message);
 
			System.out.println("Done");
 
		} catch (MessagingException e) {
			throw new RuntimeException(e);
		}
	}
}