After nearly 2 years of uninterrupted service, email stopped flowing in or out of our Exchange Server 2007 which sits on a Comcast cable connection behind a Cisco ASA5505. I started digging and reading, especially here, and decided to try switching the send connector to port 587. Outbound mail started flowing.
However, after testing open port connectivity, firewall settings, and server settings for 2 days, I have concluded inbound mail on port 25 is not going to happen. I have called Comcast 3 times and they tell me (a) there is nothing blocked, (b) their security might stop traffic on port 25, (c) incoming mail should be on port 110 (POP!?!?!).
I need some sane advice on how to approach this. The canyouseeme.org port checker doesn't even see port 25 activity if I pull the ASA5505 off the network and go through a puny linksys router (wrt54g) or just have a PC plugged straight into the cable modem. Many other common ports are reported as blocked when I try to test them as well, so I'm floundering at this point.