here is a great article on using Gmail as your smtp server. I had to do it this morning because it appears that perhaps Comcast is blocking port 25

http://mail.google.com/support/bin/answer.py?hl=en&answer=13287

here’s an additional article on chainging the default outgoing mail server on a media temple dedicated server.

http://kb.mediatemple.net/questions/83/(dv)+Change+Plesk+Outgoing+Mail+Port