Using classic Outlook for Windows in business environments
Not all Thunderbird users are encountering this unusual activity issue, but it is worth a try.
As for "I would very much like to get guidance on how to switch out of this account", it is just like removing e-mail accounts from Outlook, you can refer to this post in Thunderbird forum: How to delete an email account in Thunderbird? | Thunderbird Support Forum | Mozilla Support
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