This message appeared after installing The SMTP service on my domain controller.
I use Office 365 Exchange online and Lync Online so no legacy Exchange or Lync server to worry about
The issue turned out to be the IP address in the SMTP server properties being set to the Domain contoller IP rather than [All Unassigned] once I changed this setting and flushed the DNS on the client PC the message disappeared
This is a screen shot of the CORRECT setting