This is primarily so I can remember how to do this. I have yawl set up as a postfix host here at Chez Geek, but my smart mailhost is actually off in colocation land.
So with my problems with Thunderbird still unresolved, it was time to try setting yawl up as a smarter mail client.
First things first, make sure postfix is installed. With Ubuntu, it comes installed by default, but not enabled.
Second, set up an /etc/postfix/main.cf file, and put in there: