Deleting your att email account is like deleting all your presence with att email services, but yes you can also recover your account whenever you want to and that too a very simple and quick process. So now, the question is how to delete att email account, well you need to go to your profile, and then you need to go to some more options to complete the deletion.
I got stuck in the same problem. I tried many times to remove my email account from AT&T device but failed. I asked experts of Dissertation Help UK to help me out from it. They assisted me to go to the settings and log out my account permanently from that device.