I just clicked on the link again and it returns the following:
"The page you are looking for has moved, been replaced, or is currently unavailable.
We apologize for the inconvenience."
Also, this happens with Office 365 SMTP as well, so it's not just an AT&T problem. And besides this was all working fine and then stopped working. It seems like something happened with our Method install and how it interacts with SMTP.