It is necessary to check that ATT.net email settings for Thunderbird are set up correctly, and then make any necessary changes. How to get started: Here are the steps you can take:1. You can access the account settings by tapping the file under the account.2. To update email settings, select the account that needs to be updated.3. Enter the correct information in the POP3 and IMAP sections.4. Click OK after you've added all the values.5. To finish the process, click Finish at the end.