But I don't see where I can use a different port for my smart-host.
I setup a company many years ago with an internal email
server. I have a non-standard port on a firewall route my email to their box for forwarding, since it in not their primary machine. It will only accept forwarding from my address.
If I don't do it that way, then I need to forward through comcast's email servers, and they are HORRIBLE.