Using classic Outlook for Windows in business environments
On the subject of region, I recall that when this whole mess began, Thunderbird repeatedly threw an error about a time zone issue (unfortunately, I failed to screen grab it). I logged into my Hotmail account via outlook.live.com to confirm the time zone and it was set to an incorrect region. I would change it, but hours later, it would revert back to the incorrect zone and Thunderbird would again throw the error.
I'm just adding this info here in the hope that it might be useful for MS to finally fix this problem plaguing so many of its customers.