Rated 4 out of 5 stars

Very useful add-on indeed. I use it since a long time.
Unfortunately, it's not compatible with Thunderbird 3.0.
It can be installed normally but there is an error message when clicking on the "options" button:

Erreur d'analyse XML : entité non définie
Emplacement : chrome://folderpane/content/folderpanePref.xul
Numéro de ligne 255, Colonne 19 :

This review is for a previous version of the add-on (0.0.5.1).