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’ is not within the scope of this operation. Cannot perform searches outside the scope ‘ ’.”
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 user.name –ignonreDefaultScope”