To know device, then check out the steps as mentioned in the guide:

• From mail, choose mail > preferences.

• Select account and choose the + sign.

• Tap to add another mail account and click to continue.

• Fill up the add a mail account info:

• Full username

• AT&T email address

• Password: enter the password or secure mail key

• Choose to create, and the account will automatically configure and appear in the accounts list.

• Lastly, select the preferences window to begin using an email account.