LONG POST AHEAD - You didn't mention if this was on a workgroup or a domain, but this reply is more for a domain. On the server - Primary DNS should be the server's IP address. There should NOT be any ISP's DNS on the secondary. Like the other poster said, if you go into your fowarders tab under the DNS MMC, you can create your foward and reverse look up zones. The reverse lookup zone, is usually in the format of "x.0.168.192" In theory, that's how a lot of mail servers decide whether or not to bounce or receive mail. If it can't do a reverse look up (spammers commonly have this problem) then it gets a rejected mail from the reciepient. The client should have their server's IP on the primary DNS so when you do an Nslookup, It should now say: DEFAULT SERVER: 192.168.0.X SERVER.DOMAIN.COM(LOCAL) sorry for the long reply.
