Disable opening another user's inbox

[Levi]

Our outlook has automatically allowed everyone to open
another user's inbox from the file menu. I tried the
permissions tab, but does not help. How can I disable this
feature.

 

[Al]

My first guess is that all your users have Admin rights.
On your exchange server in the active directory you can
check each users rights to their mailbox. By default
Administrators have full rights and self has read/write
priviliges. So even though the folder right in Outlook
don't explicitly mention that Administrators have full
rights to the folders they still do.