If it fails to find the server configuration, enter them as follows then click Done: Thunderbird will attempt to discover the server configuration.

NOTE: if adding a Resource Account or Shared Email, enter the Display Name and Email Address of the Resource Account.

Enter your name and email address but do not enter your password.

Click Account Actions, then Add Mail Account.In the Home or Inbox tab of Thunderbird, click the Thunderbird Menu to the right of the Search bar then click Account Settings.Thunderbird is also a third party application and is blocked by UT O365 by default- while an exception has been granted allowing for its use with UT O365 accounts, the exception could be revoked at anytime without warning if sufficient cause is identified. We cannot guarantee that UT O365 accounts will work and can only provide best effort support. Microsoft does not support Thunderbird for use with O365 accounts which often results in significant limitations of functionality. We strongly recommend switching to the Outlook Desktop app or the Outlook Web App

Microsoft 365 thunderbird