Reverse DNS checker

Why should you use the Reverse DNS Checker application?

Our Reverse DNS Checker can look up the domain name for an IP address. It is a simple and fast tool to perform reverse DNS queries online. You can use console tools like nslookup or dig instead. Those console tools use much fewer resources and do not make any unnecessary client-server requests during the lookup. But some people might prefer to use our online application. The most frequent reasons for choosing our tool are:

• The app works on mobile devices
• Users do not have to use the console, read manuals, etc.
• It is much easier to copy results from the web page than from the console

We also have a tool for DNS lookup which could be used to get the IP address of a domain. This tool also looks up a lot of other useful information like CNAME, MX, or SRV records.

How does the Reverse DNS checker work?

We use a well-known library, DnsClient.NET, to perform reverse DNS queries. This library is known as a simple, yet powerful and performant solution. And it is definitely easy to use. All we have to do is create a LookupClient and call a QueryReverseAsync method. The library will do all the work for us. We just have to wait for the result.

So, you may wonder what is the value of our online application. Anyone could create such an app. All the hard work was already done by the author of the library. Well, it is true. But we want to create a suite of tools for email diagnostics in the near future. Email is a complex system and it uses the DNS protocol a lot. There are different types of records used to configure email delivery and security. That's why we also want to have all necessary DNS lookup tools in our application set. You can use our app, or use anything else. We need it anyway, so why not share it with you?

How can the Reverse DNS checker be used in practice?

Our user, Mike J., shared his use case with us. He uses the DNS Lookup app first to get the IP address of the domain he wants to investigate. Then he opens the Reverse DNS checker app and looks up the PTR record for the IP he got before.

You might think that this is nonsense. The reverse lookup should return the same domain he already has. But it is not always true. Actually, it is not true in most cases. Usually, website owners outsource hosting to some providers. Sometimes they have multiple websites on the same IP, or use proxy servers for caching or security purposes. So reverse lookup could return another domain, which provides some useful information to Mike.

Another interesting use case is described by our user, Kate T.. Sometimes, Kate wants to discover who sent her the email, or which servers were used during the delivery process. She uses email headers for this purpose. Sometimes, those headers include only IP addresses, but not domains. So Kate can perform reverse DNS lookups to find out the domain names. Then she can use the WHOIS tool to get more information about the domain owner. By the way, we also have a tool for such email headers analysis.