What Is IP Reputation and How To Check It

5 min read
22 November 2021
Gustavas Davidavičius

IP reputation can help determine whether or not the requests sent from certain IPs are legitimate. But how is IP reputation determined? Why does it matter? And how to check it?

What is IP reputation?

IP reputation is a measure that helps evaluate the quality of an IP address and determine how legitimate its requests are. It allows us to assess the source’s reputation and separate genuine email sending and browsing behavior from the actions of cybercriminals, hackers, bots and fraudsters. 

In short, your IP address reputation can show the quality of your emails and consequently determine the success of your email marketing campaigns. Unfortunately, without a good reputation, your messages might not even reach the intended recipients’ inboxes.

Luckily, it is possible to improve poor IP reputation. First, let’s answer a few burning questions. How is IP reputation determined? Why is IP reputation important? How can you identify a bad reputation? Once you learn more, discover how to change things around and gain a more favorable position. 

How is IP reputation determined?

You could easily compare IP reputation to a credit score. The creditor in this situation is an internet service provider (ISP). The ISP assesses your IP reputation to decide if you should keep sending and receiving requests. 

Similarly to a bad credit score, you can gain a bad IP reputation based on past actions that are checked and reviewed to determine your credibility. In this case, internet service providers can attach a bad name to IP addresses based on specific metrics, including:

  • Spam traps or honeypots
  • High bounce rates
  • Spam complaints
  • Volume of emails
  • Frequency of emails
IP reputation metrics include high bounce rates and spam complaints.
What influences IP reputation?

If IP addresses have fewer spam complaints and a low bounce rate, they have a more positive IP reputation. However, when numerous emails transmit from the same IP address, spam filters pick up on high volumes, and the address might get a negative reputation. In this case, your emails might end up in the spam folder, effectively making them useless.

IP reputation: dedicated vs. shared IPs

It’s important to mention the reputation of dedicated IP addresses and shared IP addresses are determined differently.

A graph shows the difference between shared and dedicated IP addresses.
Shared vs. dedicated IP address

If you’re using a dedicated IP address, your IP reputation is entirely based on how you yourself use it. However, if you’re using a shared IP address, the reputation is based on the common activity of all users sharing that same address.

Each email service provider (ESP) can gain a negative or positive IP reputation as well. This is based on the behavior of IP addresses owned by ESPs. If the ESP allows sending spam, the entire environment can gain a lower IP address reputation, thus affecting the email deliverability of all linked addresses. Needless to say, checking the score of an ESP is a good practice before creating your account.

Now that you know what IP reputation is, we can discuss why it matters, how to check and improve it as well as how to get an overall better sending reputation.

Why does IP reputation matter?

IP address reputation determines the quality of the IP address’s email sending environment. It also helps evaluate the overall web reputation of specific IP addresses. Consequently, your IP reputation can directly determine the success of your email campaign.

Needless to say, this is especially important for businesses that heavily rely on email marketing campaigns. If you need your emails to reach inboxes instead of ending up in spam folders, the reputation of the sending IP address must be pristine. Unfortunately, in some cases, the control of your standing might seem out of your hands.

For example, even if you don’t send spam emails or take other actions that can lead to a negative reputation, your network could be compromised and turned into a spamming platform. Your system could also be hijacked and added to a botnet for distributed denial service attacks.

One last thing to note is that there is a difference between IP and domain reputation. The latter is more related to having numerous domains. Plus, your email sending domain stays with you while the IP addresses can vary. That said, both are crucial for email marketers as both can determine your overall sender score.

How to check your IP reputation

Now that you understand why IP reputation is important, it’s time to make sure that you don’t have a bad one. You can check your IP address reputation manually or using dedicated tools.

Before you start checking IP addresses, you need to identify the IP address you’re using to send messages to your customers. To do that, you can look at any message you’ve sent and find the IP address in the header section. More specifically, under Sender Policy Framework

A magnifying glass looking up an IPv4 address.
IP reputation check

Tools to check your IP reputation

If you’re looking for real-time data, it’s far easier to check your IP address reputation using dedicated tools. Let’s take a look at a few you can use to monitor and improve your reputation:

  • Google Postmaster Tools
  • Smart Network Data Services (SNDS)
  • Sender Score

Google Postmaster Tools is a popular suite that shows how Google views your IP reputation. Because many people and businesses send messages using Gmail, it is one of the top tools to identify reputation issues. It reveals your IP address reputation, domain reputation, encryption usage, email authentication success and failure rates, and spam rates. 

Microsoft SNDS works similarly to Google’s Postmasters tool, but it’s a better solution for any company using Outlook. The tool helps you monitor your IP reputation by showing you specific data points like the reputation of your sending IP. Furthermore, it also detects malware, botnets, spam bots, viruses and compromised servers. 

Sender Score is another popular tool you can use to check your sending IP reputation. The tool reveals how mailbox providers see your IP address using a simple scoring system from 0 to 100.

A score between 0-70 indicates a bad reputation. On the other hand, a score between 70-80 is a good sign that your position could improve. A score of above 80 means your company has an excellent sender reputation. 

A gauge with an arrow pointing to a high IP reputation score.
A high IP reputation score can indicate excellent mail sending reputation

How to improve your IP reputation

You now know how to check your IP reputation. The next step is to monitor and improve it. 

If you’ve recently obtained a new IP address with a poor reputation, or you simply have an IP address with that kind of position, it’s essential to start fixing existing problems. 

If you don’t have an established reputation yet, it’s crucial to build it up slowly. This process is known as IP warming, and it helps you methodically increase email volume and, if necessary, move to a high volume sending campaign suited for your business. 

You also need to make sure that your IP address is not blocklisted. If your IP is flagged and added to a blocklist, you should contact the administrator of that list to learn how to delist your IP from their IP reputation database. 

Of course, you have to make sure you don’t repeat the same mistakes that got you into trouble in the first place. If you don’t want your IPs added to another infamous IP reputation list, here are few other things that could help improve and keep your reputation high:

  • Focus on sending emails to responsive users
  • Separate your transactional emails from marketing emails (use separate servers)
  • Make sure your servers don’t have malware 


Needless to say, IP reputation is an important metric for all companies that rely on sending emails to customers. It can make or break your email marketing campaign. Poor IP reputation can even add your IP address to a blocklist, and it is not always easy to remove IPs from those. 

Now that you know that a good IP reputation is a vital indicator you need to understand, monitor and improve, you can take action to ensure that you always score high on the reputation scale. Hopefully, the tips and tools discussed in this article will help you along the way.

About the author

Gustavas Davidavičius

Senior Abuse Prevention Specialist

Gustavas is a Senior Abuse Prevention Specialist at IPXO. He specializes in the abuse desk policies, as well as IP reputation upkeep on the IPXO’s IP leasing and monetization platform.
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