I am not sure if I should put this question on this board or the ISA board so I am going to put it on both.
I am running a router connected to a firewall connected to a single server running Windows Server 2003, Exchange, and ISA. I want to use ISA as another layer of defense so the server is multihomed. the Lan is connected to one NIC and the other NIC is connected to the firewall.
My question is this. No matter what traffic is sent, whether it is from the server or a PC on the other side of the server, it will have a source address of the NIC connected to the firewall right? because ISA is a proxy, it makes all requests on behalf of the clients? Therefore, having a static NAT translation to pass information to Exchange doesn't make sense because all traffic will have the same source IP when it gets to the firewall.
Is this correct and will this be a problem? I have a third NIC on my server and another port on my firewall, would it be better to hook this up and assign this IP address as that of the MX record, forcing all LAN traffic to go through the first NIC and all mail traffic to go through this second NIC?