Although DNS is not a component of Exchange Server 2003, it could cause significant problems for both Exchange and Active Directory. The following are several steps to start troubleshooting DNS issues:
Flush local DNS resolver cache on client by “IPConfig /flushdns”. This will flush out the negative cache on the client system and allow fresh DNS query results.
Flush DNS server cache using DNS MMC. Similar to flushing client DNS cache in concept, this eliminates server cache which may contain out dated information.
Try NSLookup to query Exchange server’s SRV record. Exchange server’s SRV record advertises the existence of Exchange service. NSLookup will help to determine if the required SRV record is missing.
Run DNSDiag to query and resolve SMTP virtual server. SMTP virtual server display name and IP address/port combination needed to be properly registered in DNS. If DNSDiag query to resolve SMTP virtual server is unsuccessful, this indicates that the SMTP virtual server entry in DNS or the SMTP virtual server settings are incorrect.
For more information about troubleshooting Windows Server 2003 DNS issues, see “Domain Name System (DNS) Troubleshooting Topics,” available at http://www.microsoft.com/technet/prodtechnol/windowsserver2003/troubleshooting/dns.mspx.