PowerDNS!

BIND is by far the most widely used DNS software on the Internet. On Unix-like operating systems it is the de facto standard. It provides a robust and stable platform on top of which organizations can build distributed computing systems with the knowledge that those systems are fully compliant with published DNS standards.

The djbdns software package is a collection of Domain Name System tools created by Daniel J. Bernstein. It includes software for all the fundamental DNS operations and several DNS debugging tools which administrators use to diagnose misconfigured remote servers. As of 2004, djbdns's tinydns component was the second most popular DNS server.

Knot DNS is a high-performance authoritative-only DNS server which supports all key features of the domain name system including zone transfers, dynamic updates and DNSSEC.