Topic Last Modified: 2006-05-03
The Microsoft® Exchange Server Analyzer Tool performs a Domain Name System (DNS) lookup to retrieve the Mail Exchanger (MX) records for a domain. If the MX records are successfully retrieved, the Exchange Server Analyzer then performs a DNS lookup to retrieve the Host (A) records of the servers that the MX records point to. If the DNS lookup operation does not return an IP address for any one of those Host (A) records, the Exchange Server Analyzer displays an error.
This error indicates that the DNS Host (A) record appears to be missing for the server. This error may cause messages destined for remote domains to back up in the Exchange server Remote Delivery queues. This error may also cause other routing or service delays.
The DNS lookup of the Host (A) record for an MX record can fail for the following reasons:
- The DNS server is down or not responding because of a network
failure or other reasons.
- The Host (A) record for the remote server is missing from the
DNS server because the record is unavailable or is incorrect.
- The DNS server is not configured to enable dynamic host record
updates.
-
Verify that the DNS server is running by doing one or more of the following checks:
- Look at the DNS server status from the DNS Administration
program on the DNS server.
- Restart the DNS server. For more information, see "Start, stop,
pause, or restart a DNS server" (http://go.microsoft.com/fwlink/?LinkId=62999).
- Verify the DNS server responsiveness by using the
nslookup command. For more information, see "Verify DNS
server responsiveness using the nslookup command" (http://go.microsoft.com/fwlink/?LinkId=63000).
- Look at the DNS server status from the DNS Administration
program on the DNS server.
-
Use nslookup to verify that the Host (A) record exists on the DNS server. For more information, see "To verify A resource records exist in DNS" (http://go.microsoft.com/fwlink/?LinkId=63001).
-
If the Host (A) resource record does not exist, manually add or modify the A resource record or configure the DNS server to enable dynamic record updates:
- Manually add an A resource record. For more information, see
"Add a resource record to a DNS zone" (http://go.microsoft.com/fwlink/?LinkId=63002).
- Manually modify an A resource record. For more information, see
"Modify an existing resource record" (http://go.microsoft.com/fwlink/?LinkId=63014).
- Configure the DNS server to enable dynamic host record updates.
For more information, see Microsoft Knowledge Base article 816592,
"How to configure DNS dynamic updates in Windows Server 2003"
(http://go.microsoft.com/fwlink/?linkid=3052&kbid=816592).
- Manually add an A resource record. For more information, see
"Add a resource record to a DNS zone" (http://go.microsoft.com/fwlink/?LinkId=63002).
For More Information
- For information about how Exchange Server 2003 uses DNS to
resolve external IP addresses, see "Transport Dependencies for
Exchange Server 2003" in the Exchange Server Transport and
Routing Guide (http://go.microsoft.com/fwlink/?LinkId=47579).
- For information about DNS name resolution, see Microsoft
Knowledge Base article 322856, "How to configure DNS to use with
Exchange Server" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=322856).
- For information about how to troubleshoot DNS, see
"Troubleshooting DNS" (http://go.microsoft.com/fwlink/?LinkId=63003).
- For information about Exchange Server 2003 system
monitoring, see "Chapter 3: System Monitoring with Exchange
Server 2003 Management Pack" in the Exchange Server 2003
Management Pack Guide for MOM 2000 SP1 (http://go.microsoft.com/fwlink/?LinkId=47573).
- For information about Host (A) resource records, see "Managing
Resource Records" (http://go.microsoft.com/fwlink/?LinkId=63004).