← Back to Glossary

Email Block List


What is an Email Blocklist?

An email blocklist (also known as a blacklist) is a list of email addresses, domains, or IP addresses that are identified as sources of spam or malicious content. Internet service providers (ISPs), email service providers, and organizations use blocklists to filter out unwanted or potentially harmful emails before they reach users’ inboxes.

How an email blocklist works

When an email is processed by an inbox provider the following takes place:

  1. Identification – organizations or systems monitor incoming emails and analyze their content, sender information, and other characteristics.
  2. Listing – if an email address, domain, or IP address is found to be associated with spam, phishing, or other malicious activities, it may be added to a blocklist.
  3. Filtering – when emails are sent, the receiving email server checks the sender’s information against blocklists. If there is a match, the email may be flagged as spam or rejected outright.

The purpose of email blocklists is to reduce the volume of unwanted or harmful emails, protecting users from spam, phishing attempts, viruses, and other malicious content. It helps maintain the integrity of email communication and enhances the overall security of email systems. It’s important for organizations and email service providers to regularly update and maintain their blocklists to stay effective against evolving threats.

How do I know if my email is blacklisted?

Use the MX Toolbox and enter your email’s domain name or IP address.

Want to receive more great content like this for free?

Subscribe to our newsletter to get best practices, recommendations, and tips for digital marketers