Java's platform independence is great, except when it...er, the user doesn't work. Take for instance JavaMail. The API is great. Who doesn't love the ability to send e-mail, and few other simple programming tricks can make your boss ooh and ah like a customized e-mail.
If you are using linux and get the following, very-google-cachable exception.
javax.mail.MessagingException: 501 5.0.0 HELO...
