Yahoo-sbcglobal emails

Hello,

I have still use my "sbcglobal.net" email address. Unfortunately I cannot access my emails, from my understanding AT&T is updating their system/servers. How long will this process take and also when will I be able to  retrieve my emails? When someone email me will they get a auto reply stating the email address is no longer valid or will I be able to see them? I know this email address is old but I still use it on a daily basis for business.

Thanks,