TSL or Connection security should be STARTTLS.

This will load and then fail. A window with server settings will pop up.

Enter your name, email address, and password.

Linux: Three bars menu > Preferences > Account Settings > Account Actions > Add Mail Account.

Windows and macOS: Three bars menu > Account Settings > Account Actions > Add Mail Account.Note: If Thunderbird does not automatically start the account creation wizard when you first open the program, open it with the following menus: If you aren't sure which email system you are on, please see All About Email at UO. Updating your password in Thunderbird for Windows.Updating your password in Thunderbird for MacOS.This article contains instructions for how to set up Thunderbird for UO email: Because of this, User Support Services (USS) is only able to offer best effort support for these clients, and certain issues may require the use of a Microsoft client in order to be resolved. There are often significant limitations in client functionality as a result. Note: Microsoft does not recommend this client for use with Office 365.

Configure thunderbird for office 365