Hi, Can you tell me how i can only disable subject for other users in room mailbox calendar ?

room mailbox has by default LimitedDetails access to calendar.

I want to restrict everyone's ability to see nothing in a room mailbox's calendar, except a few designated delegates. While I can reset the Default access to "None" and add individual delegates with AccessRight of Editor, the permissions for Default reverts back to AvailabilityOnly after 5-10 minutes. I cannot find it documented where and why it happens and I don't understand it. Not happy.

Re my previous post: it is Exchange 2013 SP1.