I discovered eMessage Archiver 4.01 on VersionTracker today. eMessage Archiver 4.01 - VersionTracker:
I am still checking it out, but this shareware solution looks like it is worth a look if you are interested in archiving your email. It was written by retired generalist in science, philosophy, and practical thinking named John Carlson. He originally built this system for his own use using AppleScript and HyperCard but has translated it to a very versatile system that allows archiving or just backup. You can select to archive based on message date, priority, and or folder settings.
