Unable to perform manual or scheduled scan on mailboxes for users from a different domain

I received an “interesting” issue last week that I thought would be good food for blogging.

The situation that a customer was facing was that they had mailboxes for users from multiple domains hosted on their mailbox server.

Forefront, by default, can only see the mailboxes for users from the domain where the machine account of the server resides, meaning we were unable to scan, using the manual or scheduled scan, any mailboxes for any user from a different domain, (Real Time and Transport scanning worked fine).

To address this, we imported the Forefront PowerShell commandlets into an instance of the Exchange PowerShell and enabled full domain visibility for this PowerShell command prompt window. After this we could scan (but not see using the Forefront PowerShell commands), mailboxes for the users from different domains.

The PowerShell commands that we used to do this were:-

Add-PsSnapin FSSPSSnapin

Set-ADServerSettings –ViewEntireForest $true

If anyone else has this setup and tests this, I would be very interested to hear if this works for you (we only tested this using the manual scan)