# What Is Reverse DNS Lookup? How It Works & How to Do It

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## Table of contents

- What is reverse DNS lookup?
- How does reverse DNS work?
- What are the uses of reverse DNS lookup?
- How to do a reverse DNS lookup
- 4 tools for reverse DNS lookup
- Final takeaway

B2B businesses know how hard and expensive it is to generate qualified leads to grow their business. They perform countless lead-generation activities and spend time and money to generate leads, nurture them, and convert them into paying customers.

While there are numerous ways to find leads, leveraging **reverse DNS lookup** or reverse IP lookup can help businesses discover their website visitors and translate the findings into potential business leads.

Curious to know more? Let’s get straight into the nitty-gritty of **reverse DNS lookup** and how you can use it to grow your brand.

## What is reverse DNS lookup?

**Reverse DNS lookup (rDNS Lookup) is a domain name system query to find a domain name associated with an IP address.** It is the exact opposite of forward DNS record lookup, which is nothing but DNS lookup,  where the DNS is queried to return the IP address of a domain name. Here's an infographic explaining how rDNS is executed between the Mail server and the DNS server:

![Reverse DNS lookup](https://res.cloudinary.com/mailmodo/image/upload/f_auto,q_100/v1715772480/strapi/Reverse_DNS_lookup_53c97f005a.png)

## How does reverse DNS work?
People usually know about the forward DNS lookup, which finds an IP address from a hostname. Reverse DNS lookup does the exact opposite of that. It uses a [PTR record](https://www.cloudflare.com/learning/dns/dns-records/dns-ptr-record/) to find the domain name using a given IP address.

**But what is a PTR record?**

A DNS PTR record (or PTR record) is a record that contains the list of IP addresses and their corresponding domain names. It fetches the domain name associated with the IP address.

Here's a detailed explanation of how reverse DNS works.

  

### 1. Query initiation

When a system needs to determine the domain name associated with an IP address, the query is initiated by entering the IP address into a DNS lookup tool or command-line interface.

### 2. PTR record lookup

The system queries the DNS servers, specifically requesting a PTR record for the IP address in question. The server then forwards this request to the appropriate authoritative DNS server responsible for the reverse DNS zone of that IP address range. The authoritative DNS server looks up the PTR record and sends it back, which in turn provides the domain name to the requesting server.

### 3. Response retrieval

If a matching PTR record exists for the IP address, the DNS server returns the domain name associated with that IP address. This domain name is typically the hostname of the mail server that sent the email.

### 4. Verification of response

The requester or the receiving mail server compares the domain name obtained from the reverse DNS lookup (PTR record) with the expected domain name provided in the sender’s email address (in the SMTP envelope or header).

### 5. Use of SPF

In scenarios like email delivery, SPF verifies if the domain name retrieved from reverse DNS matches the domain authorized in the SPF record associated with the sender's domain.

Reverse DNS is often used as part of the SPF (Sender Policy Framework) authentication process. If the domain name obtained from reverse DNS matches the domain name authorized in the SPF record for the sender’s domain, it can enhance the email’s reputation and increase the likelihood of delivery.

  

<div class="highlight-gray"> <p> <strong>💡 Related guide: <a href=https://www.mailmodo.com/guides/dns-record/></strong>What Is a DNS Record and How Do They Work in Emails?</a></p> </div>

## What are the uses of reverse DNS lookup?

Reverse DNS lookup is helpful in many cases, ranging from businesses looking to get prospects to email servers trying to identify spammers. Let's go over them in more depth.

### For B2B businesses

Reverse DNS lookup is quite beneficial for B2B companies. They can use the query to find valuable data about the people who visit their website. The most crucial factor is that these people are solution and product-aware and will most likely buy from you. Here is how reverse DNS proves to be beneficial for B2B businesses.

1.  It provides valuable data about website visitors who are likely already interested in products or solutions.
    
2.  It identifies potential leads based on visits from recognized domains.
    
3.  It helps you tailor marketing efforts towards prospects who have shown interest in specific products or services.
    
4.  It increases the likelihood of converting leads into customers due to pre-existing awareness and interest.
    

### For email servers

Email servers use reverse DNS search to find whether the email message came from a legitimate server. If the email server is unable to find the PTR record or finds the sender's server to be suspicious, the email server will reject the messages. This will, in turn, hurt the [email's deliverability](https://www.mailmodo.com/guides/increase-email-deliverability/). Here is how reverse DNS helps email servers.

1.  It verifies the legitimacy of email senders by checking PTR records and rejects suspicious emails to maintain inbox integrity.
    
2.  It improves mail delivery rates by authenticating sender domains through [SPF (Sender Policy Framework)](https://www.mailmodo.com/guides/spf/) and [DKIM (DomainKeys Identified Mail)](https://www.mailmodo.com/guides/dkim/) records.
    
3.  It helps mitigate the risk of [phishing](https://www.mailmodo.com/guides/phishing-email/) attacks and email [spoofing](https://www.mailmodo.com/guides/email-spoofing/) by ensuring emails originate from verified sources.
    
4.  It helps to maintain a positive sender reputation by enforcing stringent email authentication protocols.
    

## How to do a reverse DNS lookup

You can find the reverse DNS record in the following three ways. Let's go over them in detail.

### 1. Using the Windows command line

You have to run a simple line in the Windows command prompt to perform the DNS request. Follow these steps to do it right:

-   Open the command prompt.
    
-   Type nslookup followed by the IP address and press 'Enter.' For example, it can be **nslookup 8.8.8.8.**
    
-   Now, the command prompt will return the DNS name and the associated IP you entered.
    

![Reverse DNS Lookup on Windows](https://res.cloudinary.com/mailmodo/image/upload/v1660721724/strapi/Reverse_DNS_Lookup_on_Windows_ee26c75d98.png "Reverse DNS Lookup on Windows")

The command prompt will return an error if it is unable to find the records.

![Reverse DNS lookup error](https://res.cloudinary.com/mailmodo/image/upload/v1660721802/strapi/Reverse_DNS_lookup_error_dfc63982b2.png "Reverse DNS lookup error")

<div class="highlight-gray">
<p><strong> 💡Related guide: </strong><a href="https://www.mailmodo.com/guides/nslookup/">What Is nslookup and Its Benefits for Email Marketers</a></p>
</div>


### 2. Using a Linux terminal

You can use the dig command to perform the reverse DNS lookup in Linux.

Here's the command: **dig -x [ip_address]**

The terminal will return the domain name associated with the entered [IP address](https://www.mailmodo.com/guides/dedicated-ip-shared-ip/).

### 3. Reverse DNS lookup tools

Follow these steps to do reverse DNS lookup with online tools:

-   Go to any of the tools listed below.
    
-   Enter the IP address in the search box and search.
    

The tool will show you the DNS name of that IP. Read on to find out the pros and cons of various tools.

<div class="inline_cta"><div class="ctaBox"><div class="leftdiv"><p>Get 3x conversions with managed deliverability</p><div class="button_container"><a href="https://manage.mailmodo.com/auth/signup?utm_content=inline-cta-s&utm_term=/guides/reverse-dns-lookup/"><button class="primary_button">Try Mailmodo for free</button></a></div></div><div class="rightdiv"><img src="https://res.cloudinary.com/mailmodo/image/upload/v1712747193/strapi/Group_1110165064_1_57b7027899.png" width="290" height="230" alt="cta-img"/></div></div><div class="gradient"></div></div>

## 4 tools for reverse DNS lookup

Reverse DNS lookup tools streamline the process of identifying domain names linked to IP addresses by enabling users to enter the IP, conduct a reverse lookup, and obtain additional details such as TTL and blacklist status effortlessly.


### 1. Mxtoolbox

[Mxtoolbox](https://mxtoolbox.com/ReverseLookup.aspx) offers a range of tools to help you with your email marketing, and one of the tools includes a reverse [DNS checker](https://ralfvanveen.com/en/tools/dns-checker/). Users can access detailed results, including the domain name, Time To Live (TTL) period, blacklist status, [DNS propagation](https://www.mailmodo.com/guides/dns-propagation/) details, and subnet information.

While many basic tools are free to use, some advanced features and comprehensive reports may require a paid subscription.
![3.png](https://res.cloudinary.com/mailmodo/image/upload/f_auto,q_100/v1720775165/strapi/3_11fb56da95.png)


### 2. Whatismyip

[Whatismyip](https://www.whatismyip.com/reverse-dns-lookup/) is a fairly simple tool and doesn’t provide any additional information apart from the DNS name of the IP you entered.

This tool is ideal for users seeking a no-frills method to find their IP address without navigating through complex interfaces or needing any additional features or information.

![2.png](https://res.cloudinary.com/mailmodo/image/upload/f_auto,q_100/v1720775165/strapi/2_f36fc42d3e.png)

### 3. DNSQueries

[DNSQueries](https://www.dnsqueries.com/en/reverse_lookup.php) is also similar to Whatismyip because it also just provides the hostname and nothing else. Like Whatismyip, DNS queries maintain a simple and user-friendly interface, making it accessible for quick queries without unnecessary complexity So, if you’re just looking for the associated DNS name, you can try any of these two tools.

Some paid versions of DNSQueries might offer basic geolocation data associated with the IP address, helping to identify the approximate location of the server or device.

  
![4.png](https://res.cloudinary.com/mailmodo/image/upload/f_auto,q_100/v1720775165/strapi/4_f7a0fda6f2.png)

### 4. Hacker target

[Hacker target’s](https://hackertarget.com/reverse-dns-lookup/) reverse DNS lookup is just like other tools but with a twist. It offers a reverse DNS lookup tool with an added layer of security to deter automated processes. They don’t like robots, so you can see an “I’m not a robot” verification code you’ve to pass to know the DNS.

So, if you decide to use this tool, do it manually and don’t automate it, as robots can’t pass that “I’m not a robot” verification code.
![1.png](https://res.cloudinary.com/mailmodo/image/upload/f_auto,q_100/v1720775165/strapi/1_f6f57501d9.png)
## Final takeaway

**Reverse DNS lookup** is an underrated tool to get domain names using a single IP address. Its two most popular use cases are to generate leads and to identify spam.

There are many online tools to do reverse DNS lookups for you, and now you know which are the best ones. If a business nurtures these leads properly by consistently proving value, it can easily convert them into paying customers.

## Frequently Asked Questions

### What does reverse DNS lookup do?

Reverse DNS lookup or PTR lookup maps an IP address to a domain name. It helps identify the domain or the hostname of an IP address, which is useful for network troubleshooting, spam filtering, and security purposes.

### What is the use of a reverse lookup zone?

A reverse lookup zone in DNS is used for reverse DNS lookups. It contains a PTR record that maps IP addresses to domain names. This helps in verifying the authenticity of IP addresses and enhances network management and security.


### What is the difference between reverse IP lookup and reverse DNS lookup?

Reverse IP lookup typically refers to identifying domain names hosted on a specific IP address, often used in cybersecurity to assess website relationships. Reverse DNS lookup, on the other hand, specifically refers to mapping IP addresses to domain names through the PTR record type in DNS.

### Are nslookup and DNS lookup the same?

No, nslookup and DNS lookup are not identical. Nslookup, or Name Server Lookup, specifically refers to a command-line tool used for querying DNS servers to retrieve information such as IP addresses and virtual hosts. On the other hand, DNS lookup encompasses a broader range of tools and utilities associated with DNS operations, but it does not denote a standardized command like nslookup.


### How does reverse DNS lookup enhance email security?


Reverse DNS lookup enhances email security by verifying the domain associated with the sender's IP address. Email servers use this verification to assess legitimate mail servers, aiding in spam filtering and reducing the likelihood of phishing attacks.

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---

**Author: Suryanarayan Pal**

Suryanarayan has 7 years of experience in email marketing for B2B, SaaS, and e-commerce, specializing in email deliverability and project management.

