How to setup an att.net mail account?

I just purchased a new MacBook Air to replace my 2009 MacBook Pro that was using its last available OS, 10.11.6. The first attempt at Migration Assistant froze after 12 hours, and 6 hours later it was still frozen so I contacted Apple Care and they had me start over. After about 13 hours this attempt completed but my Mail accounts information didn't transfer over apparently. The popup window to add a new account opened when I opened the Mail program and clicked the other button and tried to enter my att.net email account. I wanted to setup a POP account, but it couldn't verify the account. The new account assistant tried to suggest using different incoming and out going servers than the servers I have in my old account or on my wife's MacBookPro. I tried to input these setting but it is still unable to verify the account. I'm positive I have everything, including the password correct. Any suggestions?