Yahoo mail and Vista, Windows Mail. I also ran it using XP that has Outlook Express. The only problem I have had with the former has been photograph. I have to run these though Yahoo if I send them from Windows mail they seem to conflict somewhere and all the recipient receives is numbers and letters instead of a photo. Nearly forgot Movies can not be sent through either. It seems there is a 2MB limit on mail sent from both. At least that's the best information I have at the moment.

This tutorial might help you:

http://helpme.att.net/article.php?item=2035

Also there is a automatic configurator in the support tool for setting up the account. Do you have the support tool? get it here:

http://helpme.att.net/article.php?item=3910