Replacement Rated 5 out of 5 stars

Quickfile was excellent, unfortunately it's not maintained any more. But there is an alternative. Check the nostalgy add-on. It has equivalent functionality but more features.
https://addons.mozilla.org/af/thunderbird/addon/2487/

Rated 5 out of 5 stars

I downgraded my Thunderbird 3.0 to Version 2, because without this add-on, Thunderbird is just half as good!