How can I install Exchange 2007 SP1 in an environment with a single-labeled DNS name?

Update available: Updated procedure to rename Exchange single label domains

Installing Exchange 2007 in an environment containing single-label domain names is not supported by Microsoft. Single-label domain names are names that do not contain a "dot" such as "root" instead of "". It is no longer recommended to use single-labeled DNS names in a production environment.This workaround/fix allows Exchange 2007 SP1 to be installed in an environment containing single-label domain names, proceed as follows:

  1. Run the Exchange Server 2007 SP1 install program.
  2. The following warning will appear: Microsoft Exchange Server 2007 setup cannot continue because this computer belongs to a domain that has a single-labeled DNS name. DNS domain name: XYZ.
  3. Do not exit the installation.
  4. Open the registry editor (Start\Run ? type: regedit) and navigate to HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\
  5. Edit the value data by changing the domain name to end with .x (or any value). For example, change the domain name "test" to "test.x"
  6. In the install program, press Retry to continue the installation.
  7. After the installation is complete, return to the registry editor and change the domain name back to its original name, in this example it would be changed back to "test".
Disclaimer: If you decide to proceed with the workaround, we would like to remind you that single-label domain names and the workaround are not supported by Microsoft. has confirmed this works in a lab environment - proceed at your own risk. 2008. All rights reserved.

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