I have a SBS 2003 server running ISA server. The external address to the
server is like smtp.server.com. My internal DNS is like server.local (AD).
Smtp.server.com which is a A record located on an external DNS server. I
need to have the local server resolve smtp.server.com to the local server
rather than the external IP address.

Is the best way to do this to create a new primary zone on the internal DNS
server for smtp.server.com? This certainly works but appears to cause a few
other issues. The other thing I thought of was to create a primary to just
server.com and then create an A for smtp. Does the same thing from what I
can see but then I need to add other records for other A records I still
want to resolve externally.