Sending mail using JavaMail library shows exception on second Mail

Question

I am trying to send a mail when the user clicks a button. But when I click the same once again, an exception occurs like

Mail Exception :Could not connect to SMTP host: smtp.gmail.com, port: 587

Properties code:

 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", "587");

Message Code:

session =
   Session.getDefaultInstance(
      props,
      new javax.mail.Authenticator() {
         protected javax.mail.PasswordAuthentication getPasswordAuthentication() {
            return new javax.mail.PasswordAuthentication( 
               MailIntegrationFromAddress.getText().trim(),
               MailIntegrationFromAddressPassword.getText().trim()); // change accordingly  
   }});
try {
   message.setFrom( new InternetAddress( MailIntegrationFromAddress.getText()));
   message.addRecipient( Message.RecipientType.TO, new InternetAddress(to));
   message.setSubject("Subject type");
   BodyPart messageBodyPart = new MimeBodyPart();
   messageBodyPart.setText("Message Body");
   Multipart multipart = new MimeMultipart();
   multipart.addBodyPart(messageBodyPart);
   messageBodyPart = new MimeBodyPart();
   String filename = FileLocation.getText();
   DataSource source = new FileDataSource(filename);
   messageBodyPart.setDataHandler(new DataHandler(source));
   messageBodyPart.setFileName(filename);
   multipart.addBodyPart(messageBodyPart);
   message.setContent(multipart);
   message.saveChanges();
   setCursor(new Cursor(Cursor.WAIT_CURSOR));
   Transport.send(message);
   setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
   JOptionPane.showMessageDialog(null, "Mail sent Successfully... :-)");

The mail function works fine for the first time but it fails while calling in the second time.

Answer 1

TLS provides authentication over an encrypted channel instead of a less-secure clear channel

Replace

props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");

with

props.put("mail.smtp.starttls.enable", "true");