How to grant a user account mailbox access

A common question I hear is how do I grant a user account full mailbox access to all mailboxes in Microsoft Exchange 2007? This seems like an easy answer, but it is a little tricky.

The easy answer is for existing users. If I want to grant the Trusted User account Full Access to all mailboxes on a specific server, I can use this cmdlet which sets it at the mailbox level:

     Get-Mailbox | Add-MailboxPermission –User “Trusted User” -AccessRights FullAccess

But, that is only for existing users. What about future users? Do I have to re-run this cmdlet every time I add a user? No, you can use this cmdlet which sets it as the database level:

     Get-MailboxDatabase | Add-ADPermission -User "Trusted User" -ExtendedRights ReceiveAs

Did you catch that? The first cmdlet is Mailbox-level and the second on is Mailbox Database-level.