Hm, I believe the creation and deletion of folders is currently still buggy. I already had another user reporting that shared folders are missing the "create" permission and in your case the "manager" user is probably missing the "delete" permissions. I will have to look into that at a later timepoint.
You can delete such a folder using the cyradm tool. Add the necessary permissions for the manager using the "sam" command and then later delete the folder using "dm".
An additional word of caution:
In case you put your server into production mode and have users running on the machine I would suggest to
never ever delete folders from the imap spool. In my experience the imap server is somewhat fragile concerning operations that directly touch the mail data structures without going through tools like cyradm. This can easily lead to complete failure of the mailbox db and that is a problem you definitely do not want to have on a productive server. It is in general a good idea to have a firm grasp of cyradm before embarking on longer journeys with kolab
Cheers,
Gunnar
