Our reverse DNS tool allows you to do a reverse DNS lookup on any IP address and see the reverse DNS (rDNS) value, i.e. you can see what domain sits at that IP address (this is why it is sometimes referred to as a “reverse IP lookup tool”). Reasons that you may want to do a reverse DNS lookup are many, however in the context of email you want to be sure that the IP address through which you send email is associated with your sending domain.

What is Reverse DNS or rDNS?

Briefly, in the email usage context, rDNS is what allows a receiving email system to take your IP address, and see if it really maps to the domain that your email is supposedly coming from. It’s like caller ID, only where caller ID determines your name from your telephone number, rDNS determines your domain name from your IP address. (Note that if you don’t have your own dedicated IP address, then the IP address through which your email is sent should reverse to your email service provider’s domain.)

If the domain associated with the IP address from which you are sending email doesn’t match what your email claims your domain should be (such as the “isipp.com” in the email that we send), or your email service provider’s domain if you don’t have a dedicated IDP address, then that can impact your email deliverability

Why You Need to Have Reverse DNS Set Up

As we’ve explained in more detail in our article on The Importance of Reverse DNS for Good Email Deliverability, having your rDNS set up properly is really important. And having it not set up properly (or at all) can have a severe impact on whether the email you send gets delivered or not.

If you check your revere DNS and find that it is not set up correctly, or at all, you will need to have it set up. If you are generally technically proficient, and specifically DNS proficient, you can follow our instructions for how to set up reverse DNS, but otherwise you should contact your web host or domain host, as it is very easy to mess up DNS and take down your whole website (or even an entire country).

How to Check Your Reverse DNS

Our tool is very simple and easy to use – you just type or paste the IP address in question into the form (make sure there are no leading or trailing spaces), and hit “submit”:

reverse dns tool

…and then it will show you where the rDNS for your IP address resolves; in other words, what domain sits at that IP address. If there are many domains all on that same IP address it will show either the primary domain, or the domain of the web host.

rdns lookup tool

If your rDNS is not set up correctly, i.e. not set up to point to your own domain, then it is likely set up to point to your ISP’s space instead, and you’ll see something that looks like this:


And if your rDNS isn’t set up at all, it will give you either the messages “{IP address} reverses to {same IP address}” or the message “{IP address) doesn’t have rDNS set up”.


You can check your own IP address here at our free reverse DNS tool.

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3 Responses

  1. I am in the process of designing my own website from a software package that is supposed to be “user friendly” for “non-techies” like me.

    Dumb question: How do I find out what my “IP” address is for my website email?

    Thanks for this tip!

  2. Go to

    http://www.whatismyip.com from the computer that is sending the email. That will give you an idea of what the outside world thinks is the ip of that machine. Now send an actual email to an account where you can see the full header of an email.

    Once you receive the email, it should have the generation ip address. If its the same as what you have above great, if not, you need a little more investigation.

  3. I used the tool whatismyip and it showed my address pointing back to my ISP, CableOne. I am trying to get a ‘Net biz off the ground, with not a whole lot of luck so far. I have tons of email advertising to do. So…how would I change the rDNS?

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