how to limit access on Personal folders/Inboxes ?

Hello all,

in our SAP BO BI 4.1 SP4  environment we have content for 3 different departments.

We want to create delegated administrators for each department.Data of departments are very sensitive, so there is requirement that Administrators of DEPARTMENT1 cannot see any objects related to DEPARTEMENT2, etc.

This is quite easy to setup for USERS,GROUPS,PUBLIC FOLDERS,CONNECTIONS,UNIVERSES.

But I cannot find a way how to setup it for PERSONAL FOLDERS or INBOXES.

Administrators for DEPARTMENT1 cannot see any inboxes/personal folders of users from DEPARTMENT2.

Thanks a lot for any ideas how to achieve this security !

Rudolf