Problems after conversion to AT&T (formerly BellSouth)

"the authentication type is not supported by Entourage"

Problem: User can receive e-mail and send newly created, blank e-mail. However, user is unable to send e-mail with attachments or reply to e-mails received or forward e-mails received.

This solution was provided in this Apple Discussions thread.

UidZero explains, I have had success with both Windows and Mac customers after having them change their MTU size. I have been using 1468 as the new value (default is 1500). The following link explains how to make this change:

http://docs.info.apple.com/article.html?artnum=303192

UidZero further states, If the MTU change works you might want to have a go at this (not needed for wired interfaces):

http://docs.info.apple.com/article.html?artnum=107474

In this thread users found:

• Not application specific...affects Apple Mail and Entourage users
• If you use a wired and a wireless router, the problem could affect just one or both of your routers.
• To test your Airport extreme router. Unhooked the ethernet connection from the Airport extreme router and plug the modem directly into your computer.
• If the wired router works, the change does not need to be applied to you wired network adapter, just the wireless (usually en1).
• Some users still are having the same issues despite the fix provided