Keeping the inbox clear of spam:
Everything there's to know about blacklists

All you need to know about how blacklists work and how to avoid them

If you're unable to deliver your emails anymore, the first thing you will probably think of is a blacklist. Your inbox still receives emails, but your outgoing emails vanish into thin air. But what caused you to end up on that blacklist? How do you fix what is wrong? And moreover, are you even on a blacklist? Email never stops sending for no reason, so you do have some issues when this happens. Most of the time, those issues were there for quite a while; they just never caught your eye before. Blacklists do not always cause these kinds of problems.

What is an email sender blacklist?

Why do blacklists exist?

How many blacklists are there?

How email senders end up on a blacklist

Odd scenarios where emails had blacklisting issues

Checking if your email is blacklisted

IP address check

Domain Reputation check

3 ways to get off a blacklist

Frequently Asked Questions about blacklists









Is my email blacklisted?

The first thing you need to know for sure is the root of your problems. Are you really on a blacklist? Bounce notifications will explicitly state if you have been blacklisted, so when you have an overview of these notifications, you could easily tell if your problem is caused by a blacklist. The IP address you use can also be checked for blacklisting, for example via this tool.

If you find your IP address or domain name on a blacklist, here is something to comfort your mind: There are a lot of email blacklists and they have a fewer impact than you might think. Only a few of those are being used so often that listing has an immediate impact. If you're troubled with a blacklist, Flowmailer will help you estimate its impact.

Even if you're not on a blacklist, problems can still arise. Big Email Service Providers like Gmail and Outlook use their own reputation system over blacklists. With a system like that, the chances of delivery depend on two factors: Your own behaviour as a sender as well as the way your receivers handle your email. Do you rarely cause bounces and are all your emails read? Or do people mark your messages as spam and do they leave their inboxes unopened?

Companies like Return Path provide insight into your reputation using sender score. Are you scoring under 90? You're in some kind of trouble. Check your sender score with this helpful tool!

Now what?

By now you've figured out what causes your troubles and it's time for some action. Basically, all troubles are caused by the sender. You might have caused it by accidentally sending spam since your WordPress website was not up to date. Or that email marketing campaign you suspected to slightly cross the line backfired. Maybe you never handled previous bounces or complaints and just kept emailing those addresses. Whatever caused it, you need to resolve it first. Because if you start by fixing the problem itself, solutions will always be temporary. Fix your delivery issues following these steps:

  • Make sure you know what's wrong. Start with registering on By doing so, you will get some helpful tips on where to find your problem. With that, the tool also provides a priority list on the impact of these factors. Are you on a blacklist? The named list will help you out with a link to more information on the issue.
  • Check if someone else is causing you problems. It's not unthinkable that you're sharing your digital environment. Say you're using a shared mail server or IP address. If the people you share this with misbehave, you will feel the consequences as well. If that happens, please contact your hosting provider. Is your problem still not solved afterwards? Well, there is not much left than to look for another solution.

When you've found the cause of your issues and fixed it, your reputation will restore in time. This could take you weeks of 'good behaviour', though. Same goes for blacklisting. The possibility to ask for a ‘delisting’  exist, but repetitive blacklisting will get harder to get delisted every time.

Email delivery with Flowmailer

Sending emails with Flowmailer gives you the safety you need. Our platform has an incredibly high reputation score since we only work with 100% correct authentication and prevent your emails from automatically resending after bounces. When experiencing immediate delivery problems, our team of experts will help you find a solution. With Flowmailer, you're sure your message gets delivered.

Everything About Blacklists, Summarized

Need help getting you off email blacklists?

Got problems with blacklists or your domain reputation score?
Reach out to us at: +31 (0) 10 307 45 50 or


Bad behaviour obviously isn't rewarding. It's why we stick to the law (e.g. GDPR) and the Code Email (DDMA). In the end, though, your recipient's opinion is far more important for inbox placement. Make sure your email doesn't get seen as unwanted or spam. You'll get your domains off a blacklist, but nasty customer experiences stick.