Topic Last Modified: 2006-05-04

The Microsoft® Exchange Server Analyzer Tool performs a Domain Name System (DNS) lookup to retrieve the Host (A) records of remote servers that the Exchange server is trying to send messages to. If the DNS lookup operation does not return an IP address, the Exchange Server Analyzer displays an error.

This error indicates that the DNS Host (A) record appears to be missing for the remote server. This error may cause messages to back up in the Exchange server Remote Delivery queues.

The DNS lookup of the Host (A) record from the remote server can fail for the following reasons:

To verify that the DNS server is online and that the Host record is present
  1. Verify that the DNS server is running by doing one or more of the following checks:

  2. 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" (

  3. 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: