I've just about completed my migration plan for installing 2013 into my 2007 environment. All of the prerequisites are done, I used the Microsoft planning tool, etc etc.
One question has come to my mind though that's unique to our environment. We use an external service for mail delivery. This service forwards mail to a virus/spam FW which has an external IP, NAT'd to an internal non-routable IP.
Then, this device forward mail to our 2007 hub transport server. Since the hub transport server role will go away, this obviously needs to point to either the 2013 CAS server, or the 2013 MB server.
I lightly understand that transport services have been divided among other 2013 roles. My question is, where to I point the spam FW to deliver mail during the migration, to the 2013MB server or the 2013 CAS server?