Rated 1 out of 5 stars

Kein Import der mbox Dateien möglich.
Nur Profil Import möglich, das nicht existiert.
Schlechte Anleitung.

This review is for a previous version of the add-on (14.0.1). 

ImportExportTools does have mbox import and export capabilities.
If you read the help (localized for all locales), there are descriptions for all of the context menus. Right click on a folder and it will give you these options.
Christopher