07-14-2012 11:57:40 AM
I have had a lot of problems with AT&T client support, but EVERY time it has worked in one direction and not the other has been due to a settings error in my account definition.
I used Outlook Express and now use Windows Live Mail, but it's possible the Microsoft dialogues for entering the settings are based on the same code. In one direction or t'other (I can't recall which) the port number switches back to a default if you check "[inbound/outbound] server requires authentication" after typing in the port number, so that's the first place I would look.
Have you tried crawling through the settings with one of their chat room reps?