You can't just change the port #, the incoming server has to be imap.comcast.net, and you should set it up as a new account in Outlook, not change an existing account.
You need to set up the account in Outlook from scratch using the IMAP settings. You don't convert a POP3 account to IMAP. They are two different versions of the same account. Once you have it set up in IMAP, you can go back and delete the POP version if you like.
Moved to it's own thread. in Email and Xfinity Connect.
I'm closing this thread. Beta is no longer relevant.