Review for Autoarchive by wang opera
Rated 4 out of 5 stars
Seems the author didn't update the addon to support sub directory for a long time now.
There are 2 new addons that can be tried:
1. https://addons.mozilla.org/en-US/thunderbird/addon/autoarchivereloaded/
2. https://addons.mozilla.org/en-US/thunderbird/addon/awesome-auto-archive/
To create your own collections, you must have a Mozilla Add-ons account.