OE6-Can you prevent custom folder deletion?

If this topic has been discussed... my apologies, but I could not find it.

We are creating a "Probable SPAM" folder and an associated rule to move messages to this folder if the subject line contains a "CCSPAM" prefix added by our ISA server. Unfortunately, our users can delete this folder. Is there a way to prevent this?

I tried setting the delete permission to "deny" on the "Probable SPAM.dbx" file, but OE still let me delete it. Also, I could not find a registry setting that protected the Inbox, Outbox, etc folders (dbx files) from deletion.

Many thanks if someone can point me in the right direction.

Dan