Email Security Blog

What is Whitelisting and Blacklisting in Email Security?

Did you know that there are more than 3.9 billion email users in the world today and that number is projected to grow to 4.4 billion by 2023?1 With quantities like that, it’s no surprise that email continues to be one of the most critical business communication tools used today. Sadly, however, phishing emails that cause theft, fraud, and data breaches continue to plague corporations worldwide.

How do companies keep themselves from falling victim to costly phishing attacks? While there are a number of best practices you can put into place, it’s good to first understand whitelisting and blacklisting and the role they play in email security.

What is Whitelisting?

Whitelisting an email address means you are approving them as a trusted sender. Adding a particular email address to your whitelist signals your email program that it is okay to keep the sender’s messages out of spam files. Your email service provider is also a good judge of which email addresses have a solid sending reputation and they help in the email filtering process. Companies sending emails will go to great lengths to make it onto your whitelist, especially considering that some of the benefits of being on a whitelist include fewer levels of email filtering.2

What is Blacklisting?

Email users or IP addresses that make it to your blacklist (sometimes known as blocklist) are identified as those who send spam. Several public blacklists exist and private blacklists are often created by Internet Service Providers (ISPs). In business, overly zealous email marketers are often among those finding themselves blacklisted. They are usually signaled out for not following good email marketing practices and may have high spam complaint rates, a history of sending to lists with inactive email addresses, or they may even use wording that is flagged as bad content. Unfortunately, regardless of the data used to create them, blacklists don’t catch everything.

Phishing Emails Can Swim Right Through

Email phishing attacks occur when an individual or company poses as a trustworthy organization in order to solicit information or entice the reader to take actions that, in the end, enable the attacker to do something harmful or even criminal. The downside of whitelists and blacklists is that the technology supporting them came about when email systems were relatively unsophisticated. In short, whitelists and blacklists can act as a first line of defense, but they are no match for sophisticated email phishing scams.

Going Beyond the Lists

Signs of fraud are harder to detect than ever and companies relying on whitelists and blacklists as their primary email security filter are setting themselves up for disaster. In fact, one single focused phishing attack can cripple an organization overnight. An investment in a cloud-based email security service that is designed to catch everything, including spam, malware, phishing threats, and more. It can save a company hundreds of thousands of dollars in revenue, not to mention the trust and allegiance of their customers. INKY® uses intelligent machine learning algorithms to catch abnormalities in emails, even threats never been seen before. Learn more about what a phishing attack can cost your business, and how INKY® can help prevent it.



INKY® is the emerging hero in the war against phishing. An award-winning cloud-based email security solution, INKY® prevents the most complex phishing threats from disrupting or even immobilizing your company’s day-to-day business operations. Using computer vision, artificial intelligence, and machine learning, INKY® is the smartest investment you can make in the security of your organization. INKY® is a proud winner of the NYCx Cybersecurity Moonshot Challenge and finalist in the 2020 RSAC Innovation Sandbox Competition. Learn more about INKY® or request an online demonstration today.