Sending messages is the most basic email need of a Java program. While email clients like Thunderbird and mailing list managers like listproc are the only common programs that receive messages, all sorts of programs send messages. For instance, web browsers can submit HTML forms via email. Security scanning tools can run in the background and email their results to the administrator when they’re done. When the Unix cron program detects a misconfigured crontab file, it emails the error to the owner. Books & Writers runs a popular service that tracks the sales rank of authors’ books on Amazon.com and notifies them periodically via email. A massively parallel computation like the SETI@home project can submit individual results via email. Some multiplayer games like chess can be played across the network by emailing the moves back and forth (though this scheme wouldn’t work for speed chess). And these are just a few of the different kinds of programs that send email. In today’s wired world, by far the simplest way to notify users of an event when they’re not sitting in front of the computer that the program is running on is to send them an email.
The JavaMail API provides everything programs need to send email. To send a message, a program follows these steps:
Messageobject, probably by instantiating one of its concrete subclasses. ...