Review for ImportExportTools by Newrone
Rated 5 out of 5 stars
This tool requires a little time in testing & getting used to, but it's worth it as I now have it set up to archive all my mails into readable .eml files (along with a searchable index) in a separate folder on a different disk to my TB mail disk.
My only suggestion would be to offer a Help manual (link from the menu?).
To create your own collections, you must have a Mozilla Add-ons account.