Trouble with iOS mail setup for AT&T (Bellsouth.net) account

After hours of troubleshooting and no resolution from either AT&T or Apple (they did try to help, especially Apple), I discovered the problem on my own: When the iPhone reproduces the Username in the manually entered Mail App, it only has the username before the @ sign. This doesn't matter for most mailservers as they're dedicated to a single domain name (i.e. gmail.com). But AT&T mailservers direct multiple domains to common att.net mailservers.

• Example: AT&T consumer email is username@att.NET but the same mailserver also handles 11 other email domains, such as @sbcglobal.net, @pacbell.net, @ameritech.net, and @currently.com. There can be multiple unique jsmith email accounts (jsmith@att.net, jsmith@pacbell.net, jsmith@ameritech.net) going to the same mailserver.

Therefore, when using IMAP or POP 3, the entire username must be entered, i.e. jsmith@att.net. In the iPhone the default username will show up as jsmith, even though on the New Account screen has the full username entered, such as jsmith@att.net. It will also come up with inbound and outbound addresses which aren't correct. They all need to be changed.

Once I solved these issues, following the steps laid out by AT&T works.

How To Set Up Email on a Wireless Device is a link to the AT&T Help Page explaining how to set up Smartphones.

Two other issues before you start:

1. At one time I could select Yahoo when configuring a new att.net mailbox on iPhone Mail. The AT&T Help Desk recommends this first. If you can do that, great, it's much easier. But I can't do it now, and I tried on multiple iOS devices (3 iPhones and 2 iPads) in March 2021. I believe it's related to AT&T's email security upgrade. I end up in a loop where I enter my username, then go to an old AT&T Secure Login for a username and password, then end up on a Change Password screen. Even if you change your password, don't bother. It results in an endless loop of returning to the login page then the change password page. A quick Google search shows lots of others can't either. So save some agita and go straight to Other when using Settings > Mail > Accounts > Add Account. 
2. This is just a guess but I think some simple, grandfathered passwords will be rejected by the mailserver, again due to the security upgrade. I had an old email address I use for sales responses. It has a 6 character password that was set up in 2007 before 8 characters was required. Even doing everything else right as stated above, it wouldn't work. So I did it again with a Secure Mail Key for the account and used that for the password. It worked. Or change to a currently accepted password, but I found the Secure Mail Key the reliable option.

Link "Create A Secure Mail Key"

Here are the steps I have been able to do on 5 different iOS devices:

1. Go to Settings > Mail > Accounts > Add Account > Other
2. Enter your user information (in the example I use John Smith)
   1. Name: John Smith
   2. Email: jsmith@att.net
   3. Password: <use a Secure Mail Key password>
   4. Description: AT&T (or whatever, this only appears in your app)
   5. Select Next. Verifying will be displayed. It likely won't find it and give you a New Account page with mostly incorrect information you need to change. (This seems like it's an Mail App issue).
3. On the New Account Page, select IMAP or POP (for POP3)
4. If on POP:
   1. INCOMING MAIL SERVER
      1. Host Name: inbound.att.net
      2. User Name: jsmith@att.net
      3. Password: <paste Secure Mail Key>
   2. OUTGOING MAIL SERVER
      1. Host Name: outbound.att.net
      2. User Name: jsmith@att.net
      3. Password: <paste Secure Mail Key>
5. If on IMAP
   1. INCOMING MAIL SERVER
      1. Host Name: imap.mail.att.net
      2. User Name: jsmith@att.net
      3. Password: <paste Secure Mail Key>
   2. OUTGOING MAIL SERVER
      1. Host Name: SMTP.mail.att.net
      2. User Name: jsmith@att.net
      3. Password: <paste Secure Mail Key>

Important: There are no separate screens for IMAP and POP. The data entered in IMAP will also be used for POP and vice versa, so be sure to enter the correct info for the protocol used. Also, the AT&T Help page identifies Ports. There is no place on the New Accounts configuration page to enter the Port. It should configure automatically if all other steps are followed. If not, there is a way to get to the ports, but that's more detailed for this help page. 

When this is complete, it will verify the date input. If successful green checks should appear. If so your device is configured correctly. You can launch the iPhone Mail app.