On April 8, 2019, Splunk announced that the Splunk Add-on for Microsoft Windows DNS would be deprecated effective July 7, 2019. If you are using this app in an on-prem Splunk Enterprise deployment, you may be able to continue using this app, but Splunk will not provide support in case of issues and we strongly recommend discontinuing use. If you are currently using this app in a Splunk Cloud deployment, it will be phased out in the near future. We strongly recommend upgrading to Splunk Add-on for Windows 6.0.0 or later, which has incorporated the functionality of this add-on as well as Splunk Add-on for Microsoft Active Directory.
https://www.splunk.com/en_us/blog/tips-and-tricks/end-of-availability-splunk-built-apps-and-add-ons.html

The Splunk Add-on for Windows DNS provides the necessary Windows DNS Server knowledge objects for a Splunk App for Microsoft Exchange or Splunk App for Windows Infrastructure deployment. The add-on helps you better understand and get the most out of your Windows DNS servers. Download the add-on to integrate into your Splunk App for Microsoft Exchange or Windows Infrastructure deployment or use it to provide DNS data to your own Splunk app.

The Splunk Add-on for Microsoft Windows DNS version 1.0.1 is not supported when installed alongside the Splunk Add-on for Windows version 6.0.0. The Splunk Add-on for Windows version 6.0.0 includes both the Splunk Add-on for Windows DNS and the Splunk Add-on for Microsoft Active Directory.