Donna
Let me give an update just for general info.
As of yesterday, I started having problems with one of my accounts. Seems ATT has been creating havoic on one of my accounts to the point to I could only get webmail for it. Appears that they locked me out of the account after password failures yesterday. Working half way this morning, with many failures.
It appears to be a server issue. Tried Mail and Outlook on one computer with same results. The iPad is working a bit better today. New user account has the same issue.
My other 2 ATT accounts have no problems.
Seems ATT for this account has issues. Can't even change the password at the ATT site.
I just wanted to update you and say that they are having problems again. Just see if you can get them to admit it though.
This is probably not your issue if it is just a sending problem, but you may have more success by updating to the latest server info as you said you have.