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rDNS (Reverse DNS) explained

So you have set up your Forward DNS. You are happy that you added all the needed DNS records, and you think you are done. Guess again! What are you missing? Just try to send an email from the domain, and immediately you will notice a problem. Your emails are going missing or to the SPAM folder because you haven’t set up a rDNS (Reverse DNS)! Luckily, now you will learn all about it.

What does rDNS mean?

The Reverse DNS is a service, a part of your typical managed DNS plan, and it allows reverse lookups. It lets you create a Reverse DNS zone, where you can add PTR records and use them as proof that the IP addresses and the domain name matches.

The Reverse DNS works with both IPv4 addresses and IPv6 addresses. You can use it with one or the other or both at the same time.

You will need proof that the PTR records provide so servers of other companies can backtrack the IP address to the domain name, and that way, to be sure that it is not a scam.

You will need the combination of A (IPv4), or AAAA (IPv6) records that map domain names and IP addresses and PTR records that have the opposite purpose, IP addresses to a domain name.

Why should we care about rDNS?

You should care about rDNS if:

  • You want your emails to arrive at their destination and check of the incoming mail server to finish successfully. You will most probably need a few more records than the PTR, like SPF, DMARC, and DKIM records.
  • If you are an IP network owner, you will need it to be able to do reverse lookups.

How to start using Reverse DNS?

  1. Get a DNS plan with Reverse DNS. The rDNS is a service that is usually missing from the free DNS plans. So, first, you will need to get a paid plan with Reverse DNS included and other parameters that you will need for your Forward DNS.
  1. Create a Primary Forward DNS zone. You will need to add the A or AAAA record that links your domain name to the IP addresses first.
  2. Create a Primary Reverse DNS zone. You can do it from the control panel of your provider. There you find the add Reverse DNS zone. Pay attention to the instruction. Usually, you will need to add a range of IP addresses in reverse.
  3. Add the PTR records. They must link the IP addresses to A or AAAA records in the Froward DNS zone. If they don’t make a match, it won’t function.

Can you check your Reverse DNS?

Yes, you can check your Reverse DNS by probing the IP addresses and see if they lead to the hostname. The easiest way to do it on most of the OSes (Linux, macOS, Windows, etc.) is to use the Nslookup command:

nslookup 192.169.1.2

Just change the IP address, in this case, is 192.169.1.2, with the one you want to verify. This one is an IPv4 address, but you can put an IPv6 address too.

If you need more information I recommend you this article: What is Reverse DNS?

Conclusion:

The Reverse DNS is a must-have when we are talking about sending emails. If you don’t set it up correctly, you might have emails that don’t arrive at the destination. That can cause missing opportunities, problems, and extra costs. You don’t want to lose money just because you didn’t set up your rDNS, do you?

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