Not stupid at all, but no my local firewall isn't blocking the connection, and neither is my server firewall (as posted above, iptables). I have a feeling the problem lies in the postfix configuration itself, but I even tried opening mynetworks to the world, the easiest way to get blacklisted, and even that didn't work... I'm banging my head against a wall here, and while I'd love to start from a clean setup, I have too many other services running on the server to wipe it and go again.