In my home lab, I have several applications that send email. Most of them run on linux (CentOS or Ubuntu).
I found the following directions to setup Postfix. I started doing this on every box and realized I was being dumb. I just need to setup one relay server. I thought about setting up a services box for this and other functions but found a distro that does everything I wanted.
I installed Zentyal and configured the mail server to relay mail through my Gmail account. Then just point all my other applications/servers at this internal relay. Problem solved. Now on to getting everything to authenticate through ldap, etc.