In the past my manager would just clone the exchange server and one of the dc's and change the network to "private" so that the clones were not on the production network. We were able to test sending email externally using this method
Since we have found out that that this is not the way it should be done and that we should be using surebackup, we were hoping to achieve the same thing.
For example, we need to install a service pack to exchange soon. We would ideally like to install the service pack on exchange in the surebackup environment first and test as much functionality as possible (including sending external email).