package abc;

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

public class SendMail {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String to="to@gmail.com";
        String from="from@gmail.com";
        final String username="from";
        final String password="password";
        Properties properties=new Properties();
        properties.put("mail.smtp.host", "smtp.gmail.com");
        properties.put("mail.smtp.auth", "true");
        properties.put("mail.smtp.starttls.enable", "true");
        properties.put("mail.smtp.port", "587");

        Session session=Session.getInstance(properties,
                new javax.mail.Authenticator(){
            protected PasswordAuthentication getPasswordAuthentication(){
                return new PasswordAuthentication(username, password);
            }
        }
                );

        try{
            Message message=new MimeMessage(session);
            message.setFrom(new InternetAddress(from));
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
            message.setSubject("Test Mail");
            message.setText("Hey I wrote a java code to send mail. Thanks ");
            Transport.send(message);
            System.out.println("Sent Mail :)");
        }
        catch(MessagingException e){
            e.printStackTrace();
        }

    }

}

javax.mail.AuthenticationFailedException: 534-5.7.14 <https://accounts.google.com/ContinueSignIn?sarp=1&scc=1&plt=AKgnsbvHc
534-5.7.14 gCjfbim5WYCDTQee6sZlZ2d31nncueOizOcz9NieexN5nSlGr0c49lSZ43qc4RQPQvpWLH
534-5.7.14 qCUQUecjIR7qxdYJ5R_WgLxkzD9u4Ds3EEG7ceSMyTZg0dpSGJb-zl5C82YDTdLOYTX5Pl
534-5.7.14 tmEfWrmktFCdAxUjtDiPNruDLqhPSIZ9dd187tQjBtOw2X8zx7MUcysN9BRawwDmbXT6mJ
534-5.7.14 cLn_sJS5UBuqommn0uJK7W1tPZzU> Please log in via your web browser and
534-5.7.14 then try again.
534-5.7.14  Learn more at
534 5.7.14  https://support.google.com/mail/answer/78754 qy7sm48619995pab.34 - gsmtp

    at com.sun.mail.smtp.SMTPTransport$Authenticator.authenticate(SMTPTransport.java:648)
    at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:583)
    at javax.mail.Service.connect(Service.java:313)
    at javax.mail.Service.connect(Service.java:172)
    at javax.mail.Service.connect(Service.java:121)
    at javax.mail.Transport.send0(Transport.java:190)
    at javax.mail.Transport.send(Transport.java:120)
    at abc.SendMail.main(SendMail.java:36)