Office365 stopped working 3 days ago with my [email protected] Account. It give an error saying user is authenticated but not connected. It will send messages through the SMTP but will not download or sync. A few months ago I had to switch the Authentication to OAuth2 and it began working again. It appears to be a similar issue. I confirmed the account is working through the browser but not with Thunderbird. I have other Office 365 accounts that work with different authentication.