Question

outlook 2003 connection problems with exchange server

VPN, connection, Exchange 2003, Outlook 2003, Outlook, VPN Tunnel, Routers, Cisco, DHCP

We are about to use the Exchange server from a parent company. We created VPN tunnels between their CIsco routers and our netscreen ones. I can ping the exchange server with its IP address 172.31.1.20 and also with its name ( email.domain.org ). When I set up the email account I enter the IP address in the exchange server name and I am able to connect. Once the names are checked and the server name is changed from its IP address to its name it won't connect any more.
Our subnet is 172.28.6.0/24 with DHCP server 172.28.6.20 and DNS servers 172.28.6.20 and 172.28.6.21.
Any ideas will be appreciated, thank you.

Thank you for your replay wrobinson,
Yes, OWA works, even from my home using PPTP
. We actually have 8 sites that are going to use that exchange server, 7 of them have the netscreen in our side . The 8th one has a CIsco ASA managed by them, this one works but athe difference is that in that site we get the DHCP from the router because there is no server there Yet. AT the begining we have the same problem in that site but then they added another DNS server and it worked. I think we have a DNS problem but I can't find out what is wrong yet.