

Click the drop-down for Authentication method and change it to OAuth2:.


Within the large white box, click your email address or existing Office365 server.From this same Account Settings navigation pane on the left, click Outgoing Server (SMTP).Verify the other settings: Server Name for the IMAP Mail Server is, Port is 993, your email address is the User Name, and Connection security is SSL/TLS.Under Security Settings, click the drop-down for Authentication method and change it to OAuth2: From the Account Settings navigation pane on the left, click Server Settings.From the pop-up menu, click Account Settings.Click the Thunderbird Menu icon (three horizontal bars) at the upper-right of the Thunderbird pane.From the Windows Start menu, open Thunderbird.
