You're trying to send from a GMail user while not using GMail*. The exception says the sender is unauthorized. Apparently either GMail or your local server doesn't like the From address. Try using GMail's own SMTP server; there are many threads about it, and I believe even an FAQ entry.
* well, that's what I'm actually assuming. The lack of any explicit SMTP host makes me think the local host is used.
Thanks for the answer Rob. I'll definitely look into it.
Bear Bibeault I totally agree with you and surely what you are telling me is correct but since I was not getting it so I wanted to ask you guys just to show me the direction. Surely you guy are doing a great job. Thanks anyways.