Perhaps we should ask the user about this at start up time or config-time, sup is after all an interactive application. Answers could be: yes/no/quit. I imagine that this will be a fairly typical error, especially since there is no way (that I can see) to specify special folders in sup-config. It is annoying if you created the special folders wrongly, things got labeled badly, or you need to mess around deleting maildirs in sync (which you'll have to do if you use offlineimap). What do you think?