I am getting inundated by junk / spam emails from numerous ".onmicrosoft.com" addresses. The existing junk filters in Thunderbird appear to be powerless to blocking all ".onmicrosoft.com" garbage. Creating a separate junk filter for every single permutation of this email address is simply too large of a task.

How about allowing a junk filter that would allow me to eliminate all ".onmicrosoft.com" addressed emails by using the convention of "*@*.onmicrosoft.com" . Where the "*" is read by thunderbird to mean anything occupying that address position.