javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 25;

The Code I'm Using to send a simple mail

import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
import java.io.*;
import javax.activation.DataHandler;
import javax.activation.FileDataSource;

public class SendMailUsingAuthentication
{

  private static final String SMTP_HOST_NAME = "smtp.gmail.com";
  private static final String SMTP_AUTH_USER = "myemail@gmail.com";
  private static final String SMTP_AUTH_PWD  = "mypassword";

  public static void main(String args[]) throws Exception
  {

  }

  public void postMail( String recipients[ ], String subject,String message , String from) throws MessagingException
  {
    try {
        boolean debug = false;

        Properties props = new Properties();
        props.put("mail.smtp.host", SMTP_HOST_NAME);
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.auth", "true");
        Authenticator auth = new SMTPAuthenticator();
        Session session = Session.getDefaultInstance(props, auth);
        session.setDebug(debug);

        Message msg = new MimeMessage(session);

        InternetAddress addressFrom = new InternetAddress(from);
        msg.setFrom(addressFrom);
        InternetAddress[] addressTo = new InternetAddress[recipients.length];
        for (int i = 0; i < recipients.length; i++) {
            addressTo[i] = new InternetAddress(recipients[i]);
        }
        msg.setRecipients(Message.RecipientType.TO, addressTo);

        msg.setSubject(subject);

        msg.setContent(message, "text/plain");

        Transport.send(msg);

    } 
    catch (Throwable e) 
    {
        e.printStackTrace();
    }
 }
/**
* SimpleAuthenticator is used to do simple authentication
* when the SMTP server requires it.
*/
private class SMTPAuthenticator extends javax.mail.Authenticator
{
    public PasswordAuthentication getPasswordAuthentication()
    {
        String username = SMTP_AUTH_USER;
        String password = SMTP_AUTH_PWD;
        return new Pa