Switch Between Email Accounts
I used to be able to sign in to all three of my att.net email accounts and switch between them. That function is no longer available. Why not? It doesn't make any sense to take away functionality when updating a system! Put that back in the system!

Hello there,
Due to contractual agreements and the nature of your issue, you’ll need to contact AT&T for a resolution. When contacting AT&T support, it is very important that you provide your full AT&T email address so that they are able to successfully locate your account in their system. Here’s how to contact them:
Call them directly – 1-800-288-2020
Go to their help site – AT&T Help Support: https://www.att.com/support/