Blacklists: Everything You Need to Know

 In Deliverability

Before you get started, click here to download our guide – “4 Easy Hacks to Stay Off of Blacklists”

Blacklists are complicated.

Although we can’t change the complexity of blacklists, we can bring some clarity to the subject. By the end of this post, you’ll not only understand what blacklists are and how they impact deliverability, but you’ll also know what to do if you become blacklisted.

Knowing what a blacklist is and protecting your email reputation are two very different things. One of the main reasons we started was to break down the myth that big enterprise marketing clouds are the only way to have email success.

You’re more than capable of doing this, and we’re simply here to help. So…

What is a blacklist?

A blacklist in its simplest form is a way of sharing information about email senders who are acting like spammers. It’s a way of crowdsourcing spam patrol. Kind of like a neighborhood watch for inboxes.

A more technical definition of an email blacklist is a real-time repository to determine if an IP address or domain is sending email that could be considered spam. In other words, blacklists are a way to quickly alert other recipients about a sender that looks like a spammer.

How does a blacklisting impact me?

If your domain or IP address is reported as someone that could be considered spam, you’ll see open rates plummet. If that happens, you could lose a lot of money. So if you drive any percentage of your business directly (or indirectly) from email, you need to know about blacklists.

Now you may be asking, what’s a “domain or IP address” and how do I make sure I don’t get reported? Great question.

A domain is a URL, like For this discussion, we’re talking about the domain your email addresses are coming from. That may be the same as your website domain, or you may use a different domain to actually send the emails.

An IP address is a location (address) of where you’re connecting to the internet via Internet Protocol (IP). It’s a unique string of numbers separated by periods that identifies the server you’re using to send emails.

For more on shared vs. dedicated IP addresses, click here. But for the purposes of this post, you should know that if you’re sending email, you’re using either dedicated IP addresses or shared IP addresses. On a dedicated IP addresses, you’re the only person/business sending emails from that location. Shared IP addresses are, as the name implies, shared among multiple senders.

As you think about blacklists, it’s important to know that they’re real-time and not set in stone. It’s not great to be on a blacklist, but if you can get on a blacklist you can usually get off of one, too.

How do I end up on a blacklist?

As we said, blacklists are complicated. The possible ways in which you can land on a blacklist is one of the primary reasons it’s so complicated.

You can land on a blacklist if you’re a spammer and you can land on a blacklist if you’ve done nothing wrong.

Before you freak out, though, we’ll break down a few of the main ways you can get on a blacklist and the severity of each violation. The three main ways to end up on a blacklist are:

  1. Poor sending practices
  2. Poor audience selection or targeting
  3. Your recipients mark you as spam


Poor sending practices

How you send emails has a direct impact on if you’re seen as a spammer. One of the most common causes of hitting a blacklist is related to how many emails you’re sending at one time.

If you only send emails once a month, but you have one million email subscribers, you have a high risk of being seen as a spammer. Real spammers carpet bomb inboxes in the hopes that some emails actually get through. If you go from zero emails sent to one million overnight, that looks like spam.

In order to combat this, make sure that you’re sending email consistently. If you don’t have enough content for three or four emails per week, take a look at your transactional messages or automated messages in order to establish consistent volume.

Automated emails are not only good for consistent volume, but they’re high-quality emails to your customers that drive email engagement and a massive return on investment.

In addition to managing your volume, be sure to only send emails your customers care about. If your click-through rates are low, consider shaking up your email content. Click-through rate really is the leading indicator of how engaging your emails are.


Poor audience selection

We’ve already discussed how you email your subscribers, but you also need to be aware of who you’re emailing.

“Well, I email all my subscribers. Is there something wrong with that?”


It sounds counter-intuitive, but just because someone subscribed to your list doesn’t mean they want your emails. That’s why we recommend taking explicit and implicit feedback from your subscribers when you’re selecting your audience.

Explicit feedback would be if someone opts into your list (Yay!) or unsubscribes from your list (Ugh!).

Implicit feedback takes a little more work to define but can provide tremendous insight to who actually wants to receive your emails. If someone opens your emails every time you push send, that implies they like what you are sending and are engaged with your brand. Conversely, if you’ve sent someone 15 emails and they have not opened or clicked any of them, it’s time to re-think how you’re communicating with that person.

Take this a step further by looking at clicks, orders, website visits, lifetime value, etc. These data points lay the foundation for company-altering initiatives like lead scoring or a CRM tool.

The reason you should remove the bad implicit behaving subscribers is because of blacklists. If you don’t remove those customers, you’re telling the blacklist curators that you are spamming people who obviously don’t want your message. Disengaged subscribers who are real people can get you in a little bit of trouble, but there are disengaged email addresses that can get you in even bigger trouble.

Introducing spam traps

A spam trap is an email address that’s known by blacklists to be inactive or not used by a person anymore. Each blacklist has its own way of creating or maintaining these spam traps, and there’s no way to know what the email addresses are.

Hitting a spam trap is a huge strike against you. It reinforces the need to use implicit behavior in your audience selection.


Your recipients mark you as spam

When you sign into your email accounts, you have the ability to flag specific emails and senders as spam. This type of feedback is another one of the reasons a blacklist will add you to the list.

Most email platforms, especially platforms that use shared IP addresses, are getting feedback about these spam complaints. If this is happening to you a lot, it may be time to look at your acquisition strategy.

How are you growing your list?

If you’ve recently turned on a list-growth campaign with a third party, investigate further. Maybe there’s a spike in the number of spam complaints when you send promotional emails vs. content emails. All of this information should be taken into account as you optimize your email channel.



How do I know if I’m on a blacklist?

There is no way to 100% know if you’re on a blacklist.

That’s because some blacklists are private. For example, Gmail has their own systems, blacklists, and algorithms that factor into their deliverability to the spam folder, inbox, promotional, and social folders.

The good news is that there are plenty of public blacklists where you can search for your IP addresses and domains to see if you’re listed. But, there are hundreds of blacklists, which makes it nearly impossible to monitor your reputation manually.

There are several tools that are specifically designed for monitoring blacklists and deliverability issues on your behalf. They will alert you to blacklistings when they happen and provide instructions on how to remove them.

Two well respected self-service tools for people getting started with blacklist monitoring are MxToolbox and HetrixTools. Both tools provide additional services, but blacklist monitoring is core to their offerings.

If you think you need a more sophisticated, enterprise-level solution with additional analytics and features, you may want to consider 250ok and ReturnPath. The primary feature you pay for with these vendors is called “Inbox Placement” reporting. It provides insight into where your emails go once they are delivered. i.e., the junk folder or the primary inbox.

How do I get off of blacklists?

It’s never fun to realize that you’re on a blacklist, but if it happens, don’t panic.

There are a few simple steps to follow that will help you get removed from a public blacklist. Please note this isn’t a guarantee that you’ll be removed, but following these steps and improving your sending practices and audience selection usually does the trick.

The process and outcomes will vary based upon if you’re on a shared or dedicated IP.

If you’re on a shared IP

Don’t be alarmed, this is extremely normal. You likely didn’t have much to do with being on the blacklist because there are usually dozens of clients or more on any given IP address. I would start by contacting your email provider to help you resolve this issue.

If the IP address isn’t the problem but your domain is, ask them to double check your DKIM and SPF configurations. Or, you can check them yourself using MxToolbox. If those all check out, you may have an audience or sending practice problem.

Depending on the quality of your email provider, they’re likely aware of the IP address issue and are working to resolve it on your behalf. Should you see that problems persist over time, consider switching to a dedicated IP if your volume is above 250,000 sent per month and you deploy three or more times per week. If that’s not an option, it may be time to start looking at other email vendors.

If you’re on a dedicated IP

The good news is that you’re fully in control. Start by following the instructions for being delisted provided by HetrixTools or MxToolbox. Those are manual delisting processes, but usually can be submitted in five to ten minutes.

The issue may be resolved within the hour or additional information may be required, depending on the severity of your violation and the number of violations. Stay persistent and do everything you can to stay clean during the review period.

How do I stay off of blacklists?

Glad you asked! Click below to download our guide.

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