Ok, this may not be directly an exchange 2003 question but it's a good place to start.
My scenario is this.. single exchange 2003 server... runs just fine. Mail routes correctly to internal and external people. Everyone is able to send and receive.
Now, we've a static VPN through a vpn box setup with another company. We want to send their mail down this tunnel instead of through our ISA server which all other mail routes through.
We created a DNS entry for the other companies domain. Added an MX record pointing to their mail server. Added the mail server A record to point to the correct IP address. Added the route to the other mail server on our exchange server.
I can't think of anything else to do. The exchange server should query it's DNS servers for the MX of the other company and receive the one we set in our DNS, then ask how to get there... it will get the route there through it's routing table and send the mail. The problem is that somewhere this is breaking.
Mail sent to the other company is stuck in the queue.
Our domain abc.com
Other domain xyz.com
Dns server: dns.abc.com
MX record set for xyz.com to fish.xyz.com
fish.xyz.com = 123.456.789.123
Ip of vpn appliance 987.654.321.987
Route added to exchange.abc.com
route add 123.456.789.123 987.654.321.987 mask 255.255.255.255
Obviously names and numbers and fictional but that's the setup.
I can ping the other mail server and telnet to it but cannot send mail through exchange to it.