Invalid DNS Domain Name

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2008-11-17

The Microsoft Exchange Analyzer Tool queries the Active Directory directory service to determine the value of the ComputerNameDnsHostname attribute. The value of the ComputerNameDnsHostname attribute represents the fully qualified domain name of the destination computer.

If the Exchange Analyzer determines that the Domain Name System (DNS) domain name set on the local computer is invalid, the Exchange Analyzer displays an error.

This error means that the DNS domain name contains characters other than 'A-Z', 'a-z','0-9', '.' and '-'.

To resolve this issue, determine whether the invalid characters are in the local computer's machine name or the actual DNS domain name.

  • If the invalid characters are in the machine name for the local computer, reset the DNS domain name for the domain on the local computer by using only valid characters in the range of 'A-Z', 'a-z','0-9', '.' and '-', restart the computer, and rerun Exchange Server 2007 setup.

  • If the invalid characters are in the organization's DNS domain name, consider the feasibility of renaming the DNS domain or installing Exchange 2007 into a new domain tree.


    Changing the DNS domain name can significantly affect your whole network. Before you make any change to the DNS domain name, coordinate with you network administrator.

To verify the DNS domain name of the local computer

  1. Right-click My Computer, and then click Properties. The System Properties dialog box will appear.

  2. Click the Computer Name tab.

  3. Click Change. The Computer Name Changes dialog box will appear.

  4. Click More. The DNS Suffix and NetBIOS Computer Name dialog box will appear.

  5. Verify that only characters in the range of 'A-Z', 'a-z','0-9', '.' and '-' are used.

  6. Select the Change primary DNS suffix when domain membership changes check box.

  7. Click OK to save any changes, and then click OK to exit the Computer Name Changes dialog box.

  8. Click OK to close the System Properties dialog box, and then restart the computer for any changes to take effect.

For more information about DNS names, see Microsoft Knowledge Base article 909264, "Naming conventions in Active Directory for computers, domains, sites, and OUs" (