I've spent the day composing postfix configuration. I'm retiring Rigel in favor of Sarin and Mintaka.. Mintaka is a mac mini server, and is going to be the new mail server. So, I'm integrating Rigel's ancient postfix config with OSX Server's default postfix config, updating the relevant bits, and modifying things to fit within the OSX space. Still not sure how I'm going to do the TLS setup, but we'll see how it goes.