Reverse DNS allows you to define what domain or subdomain your IP addresses come back to in a lookup. There are additional benefits to defining an rDNS record in various apps and games, with our favorite example being Minecraft. Because of Minecraft's cross-checks against their EULA blacklist, servers without an rDNS record can take much longer to ping and respond on the multiplayer server list. In addition, mail servers and some bots may experience issues without rDNS defined.
To define your rDNS records on SynergyCP, simply access your server on the panel, navigate to your server, and find the rDNS Management box. You will need to expand it.
Once expanded, you will see the following:
As shown, you should define the domain(s) or subdomain(s) per IP address, then click Save. Note these domains or subdomains technically don't need to exist, and that you can define the same domain or subdomain for multiple IP addresses.