In order to grant a user read access permission to other user mailbox we need to use the:
Add-mailboxpermission cmdlet in Exchange 2007 Shell
In this example I’ll give User A, a read access permission to User B mailbox.
[PS] C:\>Add-MailboxPermission -Identity “UserA” -AccessRights
readpermission –user “UserB”
We can also assign the following permission with the –AccessRight :