Reverse DNS, often shortened to rDNS or PTR, is a DNS record that maps an IP address back to a host name. It is commonly used for mail servers, logging, network diagnostics and reputation checks. Customers usually encounter reverse DNS when setting up outbound email, configuring a server, or troubleshooting why messages are being marked as suspicious or rejected by receiving mail systems.

Unlike a standard DNS record, which points a domain name to an IP address, reverse DNS works in the opposite direction. A receiving service can look up the IP address of the sending server and check whether that IP resolves to a meaningful host name. In many cases, especially for email delivery, this helps confirm that the sending server is configured properly and is not pretending to be something else.

DNS normally converts names such as mail.example.com into IP addresses so devices know where to connect. Reverse DNS uses a special type of record called a PTR record to do the opposite. Instead of asking “what IP does this host name use?”, the question becomes “what host name is assigned to this IP address?”.

Reverse DNS is especially important for outgoing mail servers. Many receiving mail platforms perform an rDNS check as part of their anti-spam process. If the sending IP address has no PTR record, or if the PTR record points to a misleading or unrelated name, the mail may be filtered, delayed or rejected.

A reverse DNS record does not replace your normal DNS records. In most cases, it works alongside them. A common best practice is to make sure the host name used in the PTR record also has a forward DNS record, usually an A record, pointing back to the same IP address. This is sometimes called forward-confirmed reverse DNS.

Common situations where reverse DNS may be needed include:

* Setting up a server that sends email directly from its own IP address.

* Configuring a business application that sends alerts, invoices or notifications by email.

* Improving the legitimacy and trustworthiness of a mail server.

* Troubleshooting mail delivery issues or IP reputation concerns.

Before requesting or configuring reverse DNS, make sure you have the following information available:

* The public IP address that needs the reverse DNS record.

* The fully qualified domain name you want the IP address to resolve to, such as mail.example.com.

* Access to manage the forward DNS zone for the domain, so you can confirm the host name points back to the same IP address if required.

* Confirmation that the IP address is controlled by Apexhost or by the provider responsible for managing reverse DNS on that network.

* A clear reason for the change, especially if the record is being requested for email delivery.

When a service checks reverse DNS, it takes the IP address and queries the reverse lookup zone associated with that address. If a PTR record exists, the lookup returns the assigned host name.

For example:

* Forward DNS: mail.example.com → 203.0.113.25

* Reverse DNS: 203.0.113.25 → mail.example.com

When both directions are configured sensibly, the result is more consistent and trustworthy. This is particularly useful for email systems, which may compare the sending server name, reverse DNS, HELO or EHLO name, and SPF or DKIM-related settings as part of their validation process.

1. Identify the public IP address that requires the reverse DNS record.

2. Decide which host name the IP address should resolve to. In most email-related cases, this is a dedicated mail host name such as mail.yourdomain.com.au.

3. Confirm that the chosen host name already has a forward DNS record pointing to the same public IP address, or arrange for that record to be created first.

4. Confirm who controls the IP address block. If Apexhost manages the relevant service and IP allocation, contact Apexhost Support with the IP address and the required host name.

5. Request the PTR record update and clearly specify both values to avoid delays.

6. Allow time for the change to be applied and for DNS propagation to occur.

7. Test the reverse DNS record using a DNS lookup tool or command-line utility after the update has been completed.

[Screenshot: Example reverse DNS lookup or DNS management reference]

* Use a real, fully qualified host name rather than a generic or unrelated name.

* Keep the PTR record aligned with the actual service running on the IP address.

* For email, make sure the server’s announced host name and DNS settings are consistent.

* Avoid using your root domain as the PTR target if a dedicated host name is more appropriate.

* Remember that reverse DNS alone does not guarantee successful email delivery. Other records and server reputation still matter.

Related DNS and mail settings may include SPF, DKIM, DMARC, MX records and A records. Reverse DNS is one part of a broader email authentication and server identity setup.

Reverse DNS is not resolving

The PTR record may not have been created yet, the wrong provider may have been asked to make the change, or the update may still be propagating. Confirm who owns the IP address block and re-check the lookup after some time has passed.

Email is still being rejected after reverse DNS was added

Reverse DNS is only one part of mail server trust. Check whether the host name resolves forward to the same IP address and review related records such as SPF, DKIM and DMARC. Also check the server’s HELO or EHLO name and the reputation of the sending IP address.

The host name in reverse DNS does not match the service

This can cause trust issues for receiving systems. Update the PTR record so it points to a host name that accurately reflects the service using the IP address.

What is a PTR record?

A PTR record is the DNS record type used for reverse DNS. It maps an IP address back to a host name.

Can I create reverse DNS in my normal DNS zone?

Usually no. Reverse DNS is generally managed by the provider that controls the IP address range.

Do I need reverse DNS for a website?

Not usually for basic website hosting alone. Reverse DNS is most commonly needed for mail servers and certain server administration or networking tasks.

Does reverse DNS improve email delivery?

It can help, especially when combined with correct forward DNS and email authentication records. Many receiving mail systems expect properly configured reverse DNS on sending IP addresses.

Need More Help?

If you require further assistance, please contact Apexhost Support at support@apexhost.com.au.