Virtualmin is configured to setup DNS zones but this system is not setup to use itself as a DNS server

Failed to save enabled features : Virtualmin is configured to setup DNS zones, but this system is not setup to use itself as a DNS server. Either add 127.0.0.1 to the list of DNS servers, or turn off the BIND feature on the module config page.

This is a generic error telling the website administrator that the local DNS entries are being checked using external methods. Most of the time, this wont be a real issues but it causes a performance spike which depends highly on where the DNS entries are being searched.