With a primary member ID email address, you can create up to 20 subaccount Member ID email addresses at no extra cost.
A subaccount is a member ID email address set up under the account owner’s member ID. Only the account owner can create and manage subaccounts. For example, the account owner would have a primary member ID, and their spouse or children would have subaccount member ID.
Heads up: Free AT&T email accounts that aren't associated with a home internet service from AT&T can't create subaccounts.