Forward DNS turns a name into an address. Reverse DNS turns an address back into a name.
WHAT A PTR RECORD IS
The record that says a given IP address belongs to a given hostname. It is held by whoever controls the address block, not in your own DNS zone.
WHY IT MATTERS
Receiving mail servers frequently check that the sending IP has a valid reverse DNS entry, and that it matches the hostname the server announces itself as. A missing or mismatched PTR is a common reason for mail being rejected or filtered.
ON SHARED IPS
Reverse DNS is set to the server's hostname and applies to everyone on that address. It is already configured correctly and needs no action from you.
ON A DEDICATED IP
You can request a PTR record matching your own mail hostname. This is one of the genuine benefits of a dedicated IP for anyone sending significant mail.
HOW TO REQUEST IT
Open a ticket with the dedicated IP address and the hostname you want it to resolve to. That hostname must also have a forward A record pointing back at the same address.
