Stavane
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  2. Reverse DNS (PTR) for your addresses

Reverse DNS (PTR) for your addresses

Every address of your server can answer with a name when somebody looks it up backwards. That is the PTR record, or reverse DNS. Mail servers check it: a mail from an address whose reverse name does not match is often refused or treated as spam.

What it says at the start

A new server starts with a name of ours on its addresses, like s1a2b3c4d5e6f.ams.ep.stavane.com: the code of the server and its location. It tells whoever looks it up that the address belongs to a server with us. Replace it with your own name whenever you like.

Set it

  1. Open the server in the console and go to the Network tab.
  2. Under Reverse DNS, choose Edit next to the address you want to name. Your server has an IPv4 and an IPv6 address, each with its own name.
  3. Fill in the name under Answers with, for instance mail.example.com, and choose Save.

It is a full name with at least one dot in it. localhost or server1 is refused.

Point the name at the server as well

A reverse name that points at a name which does not lead back to the same address helps you nowhere. Set both:

  • An A record for IPv4 (or AAAA for IPv6) at your own DNS provider, pointing at the address of the server.
  • The reverse name here, pointing at exactly that name.

When it takes effect

We send the change to the network straight away. Where the network has to approve a name first, the console shows Waiting for approval until it is set. Other parties keep an answer for as long as its lifetime says, so give it an hour before you conclude that something is wrong.

For mail

Mail asks for more than a matching name: an SPF record, a DKIM signature and a DMARC policy for your domain. Reverse DNS is the part that lives with us; the rest lives at your DNS provider. On level 0, outgoing mail on port 25 is closed; see Levels and limits.