In a multi-domain forest you may see the following error when attempting to use some Exchange PowerShell commands from a child domain.

“The requested search root domain.local/Users’ is not within the scope of this operation. Cannot perform searches outside the scope ‘child.domain.local’.”

Executing the following command will allow the your commands to succeed.

“Set-AdServerSettings -ViewEntireForest $True”

Additionally, you may add “–ignonreDefaultScope- “ to the command that you are trying to run.

“get-mailbox –ignonreDefaultScope”