I am trying to use Bill the Lizard's code to send an email using Google Apps. I am getting this error:

Exception in thread "main" javax.mail.SendFailedException: Sending failed;
  nested exception is: 
    javax.mail.MessagingException: 530 5.7.0 Must issue a STARTTLS command first. f3sm9277120nfh.74

    at javax.mail.Transport.send0(Transport.java:219)
    at javax.mail.Transport.send(Transport.java:81)
    at SendMailUsingAuthentication.postMail(SendMailUsingAuthentication.java:81)
    at SendMailUsingAuthentication.main(SendMailUsingAuthentication.java:44)

Bill's code contains the next line, which seems related to the error:

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

However, it does not help.

These are my import statements:

import java.util.Properties; 
import javax.mail.Authenticator;
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;

Does anyone know about this error?