I like what I'm reading about "fdm", but I don't know if I'm missing something that would make it more difficult than I think to implement.

http://fdm.sourceforge.net/

fdm is a program to fetch mail and deliver it in various ways depending on a user-supplied ruleset. Mail may be fetched from stdin, IMAP or POP3 servers, or from local maildirs, and filtered based on whether it matches a regexp, its size or age, or the output of a shell command. It can be rewritten by an external process, dropped, left on the server or delivered into maildirs, mboxes, to a file or pipe, or any combination.

[...]

5.8 From maildirs and mboxes

Fetching from maildirs allows fdm to be used to filter mail on the local machine. This is covered more detail in the later section on archiving and searching.

[...]

Thunderbird apparently uses the "mbox" format.

The only thing keeping me from downloading it and trying it out is that it doesn't have a Win32 port, so I'll have to get Kubuntu running on the desktop I would use as the "server" for this. It also doesn't explicitly say that remote mbox files on the network can be processed, but I assume if that is a limitation, then something clever can be done with local copies.

Thanks again.

Cheers,
Scott.