Can’t send email via AT&T account

Have an AT&T email account on 3 computers. Two of them running windows 10. One mqchine running windows 11. On the windows 11 machine, we set up a new email account and it doesn’t work. Sometimes you cannot send or receive. We delete that account and create a new one and sometimes it receives but does not send. It asks us to retry or enter a new password. We enter the password and still fails to authenticate. We tried setting it up as POP other times as SMTP. Still fails. Sometimes we get a yahoo pop up to help us set up the new email account but most times that yahoo pop up does not appear. We tried to match the setting of the windows 10 computer exactly and still doesn’t work. Sometimes we get it to work using the above methods but fails after 1-2 weeks. Any insights?