Outlook365 SMTP problem (Linux)

Hi,

10+ year TBird user, first post.

Current: version: 94.4.1

Our company recently changed our email server to a multi-user, Office365 account. I currently have to use the browser to send email because I cannot get the Thunderbird outgoing server to authenticate properly. Incoming mail is working fine.

The SMTP settings are (as specified by Microsoft):
Server: smtp.office365[.]com
Port 587
Connection Security: STARTTLS
Authentication Method: OAuth2

When the smtp connection is made for the first time, Thunderbird’s internal browser opens and asks for the account password. Subsequently, upon entering the correct password, it sends me a text with the six-digit code, which I enter. All appears exactly as it should but, as the send is further processed, it hangs… eventually throwing an error that the user/password combination is invalid.

I should note that I have attempted multiple other approaches including other authentication methods and security protocols The settings above are the only ones that reached the usual, first-time authentication browser dialog that Outlook users see.

How can I get Thunderbird to send my mail from this Office365 account? Is there a configuration detail I am not addressing?