We just came across an issue the other day that If our users found out could cause some serious harm. Somehow anyone with an exchange mailbox can open anyone else's mailbox including calendar. When I went into Mailbox Rights under the Exchange Advanced tab in AD I noticed that there were quite a few users that had access to my particular mailbox. However when I tried to remove them I would get the following message:
"You can not remove "Everyone" because this object is inheriting permission from its parent directory. Turn off the option for inheriting permissions, and then try removing again."
How can I fix this so that I can remove "Everyone" from being able to view everyones mailbox?