What does a PTR record do? And how to add one?
* IP address -> host.domain.com

A PTR record is a pointer.
Where an A record maps a hostname to an IP address, a PTR record maps an IP address to a hostname.

To add a PTR record in the Cobalt RaQ DNS, just go into the domain you want, and click the "Add" menu, then select "PTR record".

The only thing to make sure of is that the DNS control of your IP range has been delegated to your nameservers, otherwise it won't work.
If you are hosting your RaQ with a co-lo provider and don't have your IPs but are using the ones they provided to you, then you will have to get them to create PTR records for you.

Otherwise if you own your own subnet, make sure it has been delegated to your nameservers in order to get it working.

Lozzmo