But I have invested about 7 1/2 hours and, were it not for my persistence in requesting a supervisor I'd still be trying to figure this out.

She did a factory reset of the system and disabled then re-enabled Port 25. So I had to go back through Tier 1 and then Tier 2 and then waited about 1/2 hour to speak to a supervisor who finally took my issue seriously. This time, they wouldn't let me talk to AT&T Connect without a paid subscription. He said it should have been open by default. When they implemented the change, they didn't open Port 25 which allows 3rd party emails access. He immediately knew what the problem was. After about 6 hours of troubleshooting I finally got to a technician at AT&T Connect (paid support) even though I don't have a paid subscription. But it was a problem that was caused when they 'upgraded' my service. It took about 7 hours to troubleshoot the problem and AT&T Customer (no) Service was HORRIBLE! They kept saying they didn't support 3rd party emails. Suddenly, my Office 365 email wouldn't send or receive via Outlook 2013. Yesterday, I 'upgraded' our service from 50 mb to 100 mb. the technician discovered that some back end set up was not completed. After several technician visits, swapping hardware, etc. I initially had this problem a year ago when I first got AT&T Internet. This is a bit old, but I have some information that might help.

0x800ccc1a outlook 2013