I have Outllok 2003 also and stopped being able to retrieve messages last Wednesday night. Did the changes you made to the POP server (adding the IP address) help? Anything else you learned that might be useful? Comcast Tier 2 tech support basically told me I'm SOL and to call Microsoft. Yeah right.
My POP3 with Outlook 2013 also stopped sending emails. Comcast reps couldn't help me, but I found the answer myself.
If you look at the orginal post with the instructions on how to set up the email account, you will notice that in the graphic they have TLS encryption on the outgoing server, but they don't tell you to do that in the written instructions. They should have because this is change from their previous set up (which was no encryption).
As soon as I went into my "advanced settings" in the Outlook email set up and turned on TLS encryption for the outgoing server, my emails started sending.
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