[Dovecot] How to Prevent IMAP Folders being moved, deleted or renamed

Hello I use exim/dovecot combination for mail delivery and pickup and I'm wondering how I can prevent users from moving, deleting or renaming particular IMAP folders. I use the MailDir mailbox format.

The reason for doing this is that I have some special exim filters which deliver mail to specified directories. I don't want users to be able to change these folders because it will mess up the filtering.

Also my mail client (Thunderbird) doesn't check the filter folders automatically is there an option in dovecot that lets you send notification to clients when new messages arrive in certain folders.

more info: http://kb.mozillazine.org/How_do_I_check_for_new_messages_in_other_folders