After three months of trying to find the answer to this problem, today I
fixed it on my mom's computer. The only change I made was to enter the entire
email address, including the domain in the 'USERNAME' box. In the
instructions on the AT&T site to set up Outlook Express, it does not specify
to use the domain name in the user name. It would look like this:


You might try this and see if it works. If it does, please re-post and let
everyone know. Lots of folks are looking for the fix to this problem.