Have you ever wonder, where the heck is that permission is being inherited from??? Well here's the answer, there's some security tabs in Exchange System Manager that are hidden, so it can be useful to put them visible, for example to establish permissions to all mailboxes to the Backup user, or to do a Exmerge operation. So here come the step’s that you have to take:
1. With regedit access this key:
HKEY_Current_User\Software\Microsoft\Exchange\ExAdmin.
2. Then create a DWORD called ShowSecurityPage.
3. A value of 1 (Numeric one) means on, with 0 (Zero) means off.
4. Close the Exchange System Manger, then reopen (no need for a reboot).
After this you can right click Administrative Group-> Properties->Security Tab
This tip is also available in the follow KB article:
http://support.microsoft.com/?id=259221
