Can't Access SBCGlobal.net email. HELP!!!!

My mother is completely locked out of her sbcglobal.net email. The password is not recognized, AT&T won't help since she's not a current customer. I can't even get security questions to pop up. It says it doesn't recognize her last name. There are DECADES worth of important emails in there and just all of a sudden now it doesn't work.  No warning! HELP PLEASE!