My Att email is coming up as undeliverable

I recently found out that my email had be compromised and after speaking to customer service I was able to get my password reset and get logged back into my account, but I am not able to receive any emails.  I have been able to send emails from this account, but anytime I try to reply or send an email to that account I get a message saying "your message wasn't delivered to ________ because the address couldn't be found, or is unable to receive mail" I have been using this account for years for all of my connected Microsoft accounts as well and cannot get any of the verification codes that I need in order to be able to sign in and use my accounts again. So how do I get this account back to something that can be used as an actual email account again?