Some consider the blacklist to be the big, bad wolf—no one really knows how it looks, where it's found, or how dangerous it really is. Let’s go through all you need to know about this phenomenon.

A blacklist is a list of IPs and/or domains that are considered to be sending spam-like communication. These lists are managed by a Blacklist Operator, and ISPs* use their services to understand and classify senders.

We completely understand the fear of ending up on the dreaded blacklist. But there are hundreds of blacklists, some major and some smaller. The chances are high that you'll be on and off blacklists from time to time without it affecting your marketing noticeably. The ISPs don't always classify you as a spammer right away, they may give you the benefit of the doubt the first times. But if you stay on the blacklist they will end up classifying your emails as spam.


*ISP = Internet Service Provider or Inbox Service Provider. In this case, we use ISP as a collective term for the companies providing the email services e.g., Gmail Outlook Live and Yahoo.


Things that can lead to blacklisting

One bad email campaign doesn't mean that you end up on a blacklist. As always with emails, the whole pattern of your sending process will play an important role. It's important to have proper list hygiene and analyze your email marketing communication. Here are some factors that will affect your reputation as a sender and leads to ending up on a blacklist:

  • Your emails are marked as spam by the recipients.
  • You have a high volume of send-outs and a low volume of engagement (open rate, amount of opens).
  • Your bounce rate is unusually high for a long time.
  • You are sending to spam traps.

How to know if you are on a blacklist

It can be a bit tricky to understand if you're blacklisted but one parameter can be a noticeable drop in open rates. A drop can also indicate that your emails have ended up in other folders than the recipients' inboxes. The reasons for this are similar but in this case the ISP uses its own set of rules to qualify your sender reputation.

Another way of knowing if you are blacklisted is to use tools to monitor it. Please contact our support if you need more understanding in this matter.

How to get off a blacklist

As said, there are several types of blacklists, and they vary in size, usage and impact. Most of the time you will be removed from the list automatically as your sender reputation increases. Some of the larger Blacklist Operators will have specific instructions on how to request a de-listing. In those cases, you are required to act accordingly.

There are several tools you can use to monitor your listings—MX Toolbox (, HetrixTools ( to mention a few.

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