Create a reverse DNS record

In this article we discuss how to add a reverse DNS record (also known as an RDNS record and a PTR record) to map your server's IP address to a domain name (for example, to We use the Cloud Control Panel.


Why reverse DNS lookups?

Reverse DNS records are essential for those running a mail server since many recipient servers reject, or mark as spam, all email that originates from an "unauthenticated" server.

This means that after the sending IP address is checked, if the reverse DNS does not match the sending domain, then it is classed as “unauthenticated”.

We put ”unauthenticated” in quotes because having a Reverse DNS record attached to your domain does not automatically guarantee acceptance of email originating from your domain by the recipient's email server. It's just that non-matching or generic reverse DNS lookup settings are often rejected out of hand. Having a reverse DNS record for your domain will prevent email originating from your domain from getting immediately rejected.

RDNS can also be very useful when tracking down network issues and was the original driving force of RDNS. When pinging a website or IP address, one part of the output is the server's RDNS record.

How does it work?

When you enter a domain name into your browser, the DNS system will find the IP address of the server the domain is associated with.

A reverse DNS lookup does the opposite. It establishes what domain is associated with the IP address. This is a useful setting to configure for anyone, but it is essential for customers running an outgoing mail server on their Cloud Server.

How do I set it up?

You can easily set up reverse DNS through the control panel. Just perform these steps:

  1. Log in to your Rackspace account with the Cloud Control Panel.
  2. On the Servers tab, click the link for your Cloud Server from your Servers List.
  3. On the Server Details screen, click Add Record next to the Reverse DNS.

    Add record link for Reverse DNS under Server Details

  4. In the Add Record pop-up window:
    • Enter you domain name (for example “”) in the Hostname field.
    • Set the Time to Live (TTL) for the record.
    • Click Save Record.
  5. Back at the Server Details screen, you will now see 1 record listed next to Reverse DNS. Click this link to display the details for the reverse DNS you just added.

You can also check your settings with the dig command.

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