Check out the steps below to know the AT&T email settings for Thunderbird:
1. Tap on Settings, then File, then Account Settings.
2. Select an email account for updates, and then select email settings.
3. Choose POP and IMAP from the section and enter the values correctly.
4. After adding the AT&T email settings, tap on OK and next. Lastly, click on Finish.
With this, you have smoothly configured the settings to complete or change AT&T email settings for Thunderbird.