Can you check the Inherited Permissions in the advanced tab of the Exchange Policy for mailboxes?
If that is set to Off, check the registry for this reg key?
1.On the Archiving Service computer, start the registry editor and navigate to the following key:
HKEY_LOCAL_MACHINE\Software\KVS\Enterprise Vault\Agents
2.Create a new DWORD entry called IncludeInheritedRights a value of 1.
3.Restart the Archiving Service.
The possible values for IncludeInheritedRights are:
�0 to exclude inherited permissions
�1 to include inherited permissions