I'm running Ubuntu Server 9.10 with Postfix and Webmin.

I have created virtual hosts for 3 domains following this serverfault.com answer.

But the mail isn't relaying out to the world. I have 3 domains tied into my DNS in webmin, as well as inside DNS clicked Mail Server and followed that instruction using this article on the web.

The domains and the web servers work just fine. I also have FTP working just fine. So, the remaining problem I have is mail. Can't forward mail out to a Gmail account for some reason. Note I'm just trying to do the "easy version" of Postfix config and if your answer is in Webmin-ease, that would help me. However, I can edit a text file if you suggest.