Email Blacklist Monitoring

In Business-to-Business (B2B) communications, the efficiency and reliability of email as a communication tool are unparalleled. However, the efficacy of this tool can be significantly undermined by the presence of email blacklists. Understanding email blacklists checks, how blacklist monitoring works, and the crucial role it plays in B2B environments is essential for maintaining seamless communication channels and safeguarding the reputation of businesses.

What Are Email Blacklists?

Email blacklists, also known as DNS-based Blackhole Lists (DNSBLs) or Real-time Blackhole Lists (RBLs), are databases that track IP addresses and domains known for sending spam. Email Service Providers (ESPs) and Internet Service Providers (ISPs) consult these blacklists to filter incoming emails, blocking or flagging those considered to be spam. This process helps in maintaining the integrity of email inboxes, ensuring users receive only legitimate correspondence.

List of databases that track blocked IP addresses
List of databases that track blocked IP addresses

Unfortunately, the World we live in isn’t black and white, good and bad. Here are just a couple of examples.

  • There are several users sending emails from the same IP address. One isn’t following best practices to stay off blacklists so the IP address gets blacklisted affecting all the senders.
  • New business owner, or new employee aren’t versed in email marketing practices. They get in trouble (blacklisted) so the entire company is paying a high price.

This is why we should take both proactive measures and reactive measures such as performing email blacklist checks, or setup email blacklist monitoring.

How Email Blacklist Monitoring Works

Email blacklist monitoring is a proactive process that involves checking if an organization’s email server IP address or domain is listed on any email blacklists. Various tools and services are available for this purpose, offering features such as real-time monitoring, notification systems, and detailed reports on blacklist statuses.

A few years ago we’ve built such a service, but due to lack of interest and funding we had to shut it down. We’ve built it using our IP Blacklist API, which still remains active and users can setup email blacklist monitoring by using the API.

The monitoring process typically involves the following steps:

  1. Identification: Determines the IP addresses or domains to be monitored.
  2. Checking: Regularly scans multiple email blacklists for the presence of the identified IPs or domains.
  3. Notification: Alerts the organization if any of its email sending sources are found on a blacklist.
  4. Remediation Guidance: Provides advice or steps to remove the IP or domain from the blacklist, often involving reaching out to the blacklist operators and addressing the issues that led to the listing.
Email Blacklist Checker

3 Ways You Can Setup Email Blacklist Monitoring

  • 1. Occasionally check email blacklists manually. Set a reminder in your calendar and check if your IP address is blacklisted by performing a manual email blacklist check. Ideally, you can do this before and after a large email campaign.
  • 2. Signup at a Email Blacklist Monitoring Service. It seems that small business find it hard to justify this expense. As mentioned earlier, we’ve built such a service and found that businesses didn’t find this particularly interesting.
  • 3. Setup your own custom email blacklist monitoring service by using an API. If you are operating a large infrastructure and have a large team, you could utilize an Email Blacklist API that does the heavy lifting for you. Here’s how you can use an Email Blacklist API.

Who Should Monitor Email Blacklists?

In the B2B context, virtually every organization that relies on email for communication, marketing, or sales activities should engage in email blacklist monitoring. This is particularly crucial for:

  • Marketing departments that conduct email campaigns.
  • IT and cybersecurity teams responsible for maintaining the organization’s email infrastructure.
  • Sales teams that utilize email for prospecting and maintaining client relationships.
  • Web hosting companies and Newsletter providers send a lot of emails in particular

Monitoring is essential not only to ensure deliverability but also to protect the organization’s reputation. Being blacklisted can have a domino effect, leading to decreased email open rates, lost business opportunities, and a tarnished brand image.

Email Blacklist Monitoring
Email Blacklist Monitoring

The Critical Role in B2B Environments

In B2B environments, where transactions are often larger, sales cycles longer, and relationships built on trust, the impact of email deliverability issues can be profound. Email is a primary communication channel for proposals, contracts, project updates, and other critical business correspondences. A failure in email deliverability can lead to missed deadlines, lost revenue, and damaged business relationships.

Moreover, B2B communications frequently involve sending emails to new contacts whose email systems might be more stringent in filtering spam. This makes B2B organizations more susceptible to the consequences of being blacklisted.


Email blacklist monitoring is an indispensable practice for B2B organizations aiming to maintain effective communication channels, protect their online reputation, and ensure the success of their email marketing efforts. By implementing regular monitoring practices, businesses can swiftly address and rectify issues related to email blacklists, thereby safeguarding their email deliverability and preserving the trust and confidence of their clients and partners.


Goran Duskic has been the Founder and CEO of WhoAPI Inc. since 2011, a company that specializes in developing APIs, including the well-known Whois API. He started his career in internet entrepreneurship in 2006 and has co-founded several online businesses, including a web hosting company that he later sold. Goran's work primarily involves creating practical API solutions to meet technological needs.