Reverse DNS and PTR record – everything you need to know

Reverse DNS is a key component of the configuration of your mail server. 

Not having Reverse DNS can mean not sending emails! Without well-configured Reverse DNS zone and PTR records, the rest of the email servers can’t check your domain’s IP address and discard your messages or throw them into the spam box.

Everything you need to know about Reverse DNS

A Reverse DNS is a service that provides Reverse DNS zones for your domain. The Reverse DNS zones serve to host PTR records that can be used for verification purposes, to check the IP addresses and if they lead to the correct hostnames.

Why do you need PTR records?

The mail servers of other companies that want to send you emails need to make sure that the IP address that they are seen truly belongs to your domain. Otherwise, they can send the emails to another place, and criminals might use the information.

It is used for different services, too, for the same purpose to verify that a particular IP address belongs to the domain name.

The Reverse DNS can be used to point IPv4 or IPv6 addresses to hostnames. You can add both PTR records with IPv4 and IPv6 addresses inside the same Reverse DNS zone.

Why does the Reverse DNS matter?

The Reverse DNS matters because without it, your emails might not arrive at their destination. The mail servers of the receivers will check your PTR records, among other DNS records, and if they don’t find them, they might not trust your domain and discard the emails you are sending them.

Everything you need to know about the PTR record

The PTR record is the DNS type of record that you use for Reverse DNS and links IP addresses (it can work both with IPv4 and IPv6 addresses) to the domain name. When the receiving mail servers whats to check the origin of an email, they will perform a DNS Reverse lookup, and they will search for PTR records. The PTR records will guarantee that the IP truly belongs to the domain name.

How to perform Reverse lookup and PTR lookup?

You can perform a Reverse lookup using the nslookup command. The nslookup command is available on all popular computer OSes.

For Windows users, use the Command Prompt, and for macOS or Linux users, go for the Terminal application. There you will need to type the following nslookup command:

nslookup -type=ptr

We will specify the type of DNS record that we want, and for the Reverse lookup, we need the PTR record.

We are using the IPv4 address, but you can change it with whatever you like, so you can verify your domain or somebody else domain.

The result will be the name of the host. We can compare if this name is related to the domain we were expecting.


Now you know that Reverse DNS is and how it uses PTR DNS records to point IP addresses to domain names. Start using them for your domain and reduce the bouncing rate of your sent emails. It is not hard. It is just a matter of knowledge.

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