As we all know, sbcglobal email is powered by at&t email. So if the at&t server is down. you might face can’t sign into sbcglobal.net email problem.
So before making any changes to your account settings, first you should check the server status. If they are showing server is down. I will suggest you wait for a while and then you should try to log in again.
if at&t server status if up, but still you are going through the same problem. In that situation, you need to follow the instructions given below.
You may check the server status from: is sbcglobal server down today?