This Warning event indicates that the server could not resolve the domain for which it is authoritative in the domain records on the Domain Name System (DNS) servers it uses for name resolution. This Warning event is logged every five minutes until the server can resolve the domain in DNS.

No user action is required if this event is no longer logged. However, if the warning persists or this event seems to cause mail flow interruptions or other problems in your Exchange environment, follow one or more of these steps:

• Review the Application log and System log on your Exchange 2010 servers for related events. For example, events that occur immediately before and after this event may provide more information about the root cause of this error.
  
  
• Try to resolve the DNS issue in your Exchange environment by following these steps:
  
  
  • Use the command prompt command ipconfig /all to determine the DNS servers that are used by this server and verify that the DNS server entries are correct.
    
    
  • Determine and correct the problem that removed the domain record from the domain records on the DNS server.
    
    Note   You may be able to resolve this issue by stopping and restarting the Netlogon service on a domain controller in the domain that uses the DNS server. Restarting the Netlogon service will update the DNS entries required by Exchange Server 2010 and Active Directory if the forward lookup zone for the domain record exists in the DNS.
    
    
• Resolve your issue by using self-support options, assisted support options, and other resources. You can access these resources from the Exchange Server Solutions Center. From this page, click Self-Support Options in the navigation pane to use self-help options. Self-help options include searching the Microsoft Knowledge Base, posting a question at the Exchange Server forums, and others. Alternatively, in the navigation pane, you can click Assisted Support Options to contact a Microsoft support professional. Because your organization may have a specific procedure for directly contacting Microsoft Technical Support, be sure to review your organization's guidelines first.
  
  

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.