Most likely the SMTP server isn't configured to allow your computer to relay messages through it. I would suggest talking to the administrator of the server about that.
A cursory glance suggests its OK. But rather than relying on us as a test harness, I'd download Dumbster and test your code with it as your server. That way you will know for sure what are coding errors and what are administration/configuration issues. [ December 05, 2005: Message edited by: Paul Sturrock ]
The code looks "right" in the sense that it compiles and appears to use some APIs in the way their documentation suggests. Whether it will actually work successfully with your server is another question. Most of the JavaMail examples I see that require authentication (which you don't yet know is necessary) use an Authenticator instead of that version of the connect() method. If you haven't seen those examples, there's one here: