Users may insight here that after mid-November 2017, you are not allowed to sign in to your ATT account. Thus, in the event that you wish to access my ATT Yahoo email account, at that point you need to access the ATT account on Yahoo ATT.net. As a matter of fact, Yahoo and ATT.net get converged to give you a superior and quicker outcome. https://www.email-contactsupport.com/blog/access-att-yahoo-email-account