Comcast did not only change inbound port, they force you to send outgoing mail on port 587.
But besides changing port, they also ban personal mail servers on residential accounts. I did make changes for email to go out on port 587, but it would never work.
They force you to send on port 587, so you have no choice but to send through their mail server, at which point they control what goes out.
Only way I could get my email to work was to move my server to a co-location facility.