We have Exchange 2003 in-house in a front-end to back-end configuration. There are a number of computers joined to our domain. We have a small group of PCs that aren't. They obtain their DNS and IP through our DHCP server that serves the rest of the PCs. These PCs that aren't connected to the domain connect to a third party by way of a Juniper VPN. This VPN sets up another network connection. They use Outlook over this VPN to connect to the third party's Exchange server. This group of people has email addresses in our domain and the third party's domain. If a user sends an email, say from user@thirdpartydomain.com to user@ourdomain.com, the email goes out the outbox, but never goes anywhere. This is using our internal DNS. I've experimented with changing the DNS (on thier ethernet connection) to Google's public DNS (8.8.8.8 and 8.8.4.4) and then doing an IPCONFIG /FLUSHDNS. When I do this and send a message, it works. I can't for the life of me figure out why. Could anybody help shed some light on this? Is there anyway I can make it work using our in-house DNS by way of DHCP?