Application crash deleting IMAP-folders, that do not exist on server.

IMAP problem:
As a legacy from Apple's mail.app (I imported accounts and folders per your instruction from apple's mail.app), I have some folders (nested INBOX and other crap) in Postbox that are not on my mail server (Joyent/Textdrive - Open Solaris, mail server application unknown to me).
When I try to delete theese folders from Postbox, Postbox either copies the folder to the trash folder, or crashes. As it cannot find the folder on the IMAP-server the delete command does not work.

You should maybe write an exeption telling the user: "Folder doesn't exist on Server. The local copy will be deleted."