Check user's permission

Hi,

One of my helpdesk user administrators has specific rights on some Exchange 2010 mailboxes. For example, User1 has Full mailbox rights on mailbox User2, Read As rights on mailbox User3 and Send As rights on mailbox User4.

I need easy way (powershell script?) to find all nested rights for my specific user account, and if possible get it as single result. Can you help me with this?

Thnx!