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How to Configure Reverse DNS

Reverse DNS (rDNS), also known as a PTR record, links an IP address to a domain name, typically a subdomain. This process works in the opposite direction of regular (forward) DNS, where a domain name is connected to an IP address.

For example, if you set the reverse DNS for IP 123.123.123.123 to mail.example.com:

When you query the IP address of mail.example.com using a command like DIG, you'll receive the IP 123.123.123.123.
Conversely, performing a reverse DNS lookup on 123.123.123.123 will return mail.example.com.

Reverse DNS is often used to verify the source of an email, adding an extra layer of security. Many email servers are configured to reject or flag messages as spam if the sending IP does not have a valid reverse DNS record.

How to Configure Reverse DNS

To configure the reverse DNS, log in to the Onidel Cloud Control Panel, navigate to the service that has the IP you want to configure and click on Reverse DNS tab:

Configuring Reverse DNS

You can view the list of IPs associated with the server that have PTR records configured in the Reverse DNS Records table.

To add a new Reverse DNS record or update an existing one, input the IP address concerned and enter the domain and click Add/Update Reverse DNS.

Adding a new record will also delete any invalid PTR record has the same domain.

When you add or update a record, our system immediately checks if the A Record points to the specified IP address.

If the A record is changed after reverse DNS has been set, our system may remove the reverse DNS for that address.

Updated on: 19/06/2025

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