Your Exchange Server 2007 environment has an Edge Transport server in the perimeter network and a Hub Transport server in the internal network. You need to ensure that all external e-mail messages that are received by your Exchange environment are not impersonated. What should you do?

A.
Modify the Sender Filtering settings on the Hub Transport server

B.
Modify the Sender Filtering settings on the Edge Transport server

C.
Modify the Sender ID settings on the Hub Transport server

D.
Modify the Sender ID settings on the Edge Transport server