Have you implemented Transport and Connection handlers? Its a very good way to see what's going on - since they can be made to report Transport and Connection events. You also should turn on SMTP debugging so you can see the SMTP messages. I reckon an authentication exception would be obvious (though I can't say for sure - I've never tried to use an SMTP server that needs authentication - since authentication is not part of the SMTP spec.).
Your SMTP server (thejavahub.com) - try teleting to it and sending a mail that way. If you can do this then JavaMail should work. If you can't send to anything other than thejavahub.com addresses I'd suggest you check how your server is configured.