What is an email blocklist?

An email blocklist is a database that works to prevent email spam. Email blocklists help inbox service providers (ISPs) determine which emails should be considered spam.

Like all databases, email blocklists hold and update relevant information. If the information in the blocklist database flags you or your business, you’ll be added to the list. The list acts as a filter and prevents emails from reaching their intended inboxes.

Email blocklists are real-time databases, and there are a lot of them. Many people believe that being on one email blocklist means you’re on all the email blocklists.

This is false.

Every email blocklist is different, and ISPs value them all differently. Also, getting delisted (or removed) from an email blocklist is usually a straightforward process.

There are at least 230+ email blocklists, but there are only a handful that you should really worry about.

Here’s what you’ll learn in this post:

  • How do you know if you’re on an email blocklist?
  • How do you get on an email blocklist?
  • How do you get off of an email blocklist?
  • How do you stay off email blocklists?
  • If you’ve been on a blocklist, what does that mean for you?

Which blocklists should you worry about?

The following blocklists are highly regarded and widely used by ISPs. They are reliable and professionally maintained, and being listed on one of them may have a significant impact on your email deliverability.

  • Spamhaus (SBL, XBL, DBL)
  • SpamCop (SCBL)
  • Composite Blocking List (CBL)
  • Passive Spam Block List (PSBL)
  • Invaluement
  • Spam URI Realtime Blocklists (SURBL)
  • URIBL

Spamhaus is the gold standard of email blocklists, but all of the above are serious. If you’re on one, deal with it as fast as possible.

How do you know if you’re on an email blocklist?

There are tools out there to check the status of your server IP address. An IP address is a unique string of numbers that is unique to any individual computer or server on the network. Like a phone number or license plate.

When you press send on an email, your internet service provider (a different kind of ISP) or email service provider (ESP) connects you to one of their mail servers. The mail server then sends your email to the recipient.

Email blocklists don’t block your particular email address, they block the email server. Searching for your email address won’t tell you anything if you want to see if you’re on a blocklist.

Two recommended tools to check to see if your email server IP is on any email blocklists are:

  • MXToolbox– easy to read and understand if you’re not a technical expert
  • MultiRBL– harder to understand if you’re not technical, but more thorough

If you pay attention to your email deliverability, it’s possible to know about a blocklisting without looking it up.

Blocklist warning signs

Here are three warning signs that you’ve been blocklisted.

  1. Open rates and engagement rates plummet
  2. Email bounces increase
  3. Your ESP tells you you’ve been blocklisted

What are open rates and engagement rates?

Your open rate is the percentage of email subscribers that opened your email campaign.

Open rates will vary (a lot) based on a few factors:

The average open rates across industries will change year over year, but they hover between 20-25%

Your engagement rate is a measure of how people interact with your email. Open rates are factored into engagement rates, and include other actions:

  • Clicking links
  • Actually reading the content
  • Following a call to action (CTA)

If you’re using an ESP (email service provider), you should know your email open rates. If you pay attention to these, you’ll know when there’s a sudden change.

If your engagement rates or open rates plummet suddenly, that’s a big warning sign that you landed on an email blocklist.

Investigate the issue further by reaching out to your ESP, or looking at the individual campaign. It’s possible that the subject line or send time is responsible as well.

What are email bounces?

An email bounce happens when an email that you sent cannot be delivered.

There are two types of email bounces:

  1. A soft email bounce is a temporary issue. The intended recipient’s inbox could be full, your email could be too large, or their account might be suspended
  2. A hard email bounce is a permanent issue. The domain doesn’t exist, email address doesn’t exist, never existed, or has a typo in it.

Unlike soft bounces, hard bounces are not temporary and will not fix themselves with time. Hard bounces are a big red flag to inbox service providers that you might be spamming.

If you continue to send to hard bounce email addresses, you’ll eventually pay the price of being blocklisted.

If you see a big spike in soft email bounces, it could be a sign that you have been blocklisted.

If you see a big spike in hard email bounces, you probably just sent an email to a purchased list, and can expect to be blocklisted shortly.

“Hey, you’ve been blocklisted”

Email service providers (ESPs) want your emails to land in inboxes just as much (if not more) than you do. It’s our business. Literally.

So, if you land on an email blocklist, your ESP will tell you and help to get you off of that list as fast as possible.

“It’s our job and our responsibility to take care of the IP. In general, you’re paying your ESP to take care of that stuff, and we will take care of it for you.” – Alex Grim, Delivery Specialist at ActiveCampaign


Just because ESPs will help you get off the blocklist doesn’t mean you have a “get out of jail free” card. It doesn’t excuse you from doing things that will get you blocklisted.

How do you get on an email blocklist?

There are 3 main ways that individuals or businesses get blocklisted:

  1. Spam traps
  2. Purchased/shared lists
  3. Bad email collection processes

What is a spam trap?

Spam traps are honeypots that are used to collect spam emails and messages. Spam traps are not created to communicate with other email addresses, but to catch people who are spamming. They’re like an email sting operation.

There are 3 types of spam traps:

  1. Pristine spam traps
  2. Recycled spam traps
  3. Typo spam traps

Pristine spam traps are email addresses that were never in service. They are the ‘worst’ of the three types. These email addresses technically don’t exist, so there is no reason that they should ever be sent an email.

Pristine spam traps have never opted into a list, subscribed to a newsletter, or appeared on a business card. The only way that these emails could wind up on your email list is if you’re purchasing, renting, or scraping email addresses.

Recycled spam traps are old email addresses that haven’t been used in a long time. When an email address has been inactive, the provider will auction it off to email blocklists like Spamhaus.

From there, the recycled spam traps are sent around the internet where they end up on email lists that you can buy or scrape.

When you send emails to these email addresses, the blocklisters know about it and put your name on their list.

Recycled spam traps are the most common spam traps, and the main cause for blocklisting. These spam traps are a sign of an unmaintained email list.

It’s also possible that someone used their old email address to gain access to gated content, or to receive branded swag at a conference. If that email turns out to be a recycled spam trap, can you be blocklisted for that?

Yes. Another reason you should maintain a healthy mailing list.

Recycled spam traps aren’t as ‘bad’ as pristine spam traps, but they’re definitely not good.

Typo spam traps are exactly what they sound like. Typos.

These happen when an email is misspelled on a sign up form, or manually entered incorrectly. I would be lying if I said I had never typed “@gamil.com” instead of “@gmail.com” when I was in a hurry.

Purchased & shared lists

You should never purchase an email list. Ever.

Purchased lists will get you blocklisted.

Email blocklisters have thousands of spam traps at their disposal, and have ways to get them onto lists that people buy. They put spam traps on websites that get scraped for email addresses.

If you do buy or scrape a list of email addresses, chances are that you have some spam trap emails – and it’s only a matter of time until you get labeled as spam.

Email list renters, purchasers, and sharers are much more likely to be blocked. (Source)

Purchased lists are bad for everyone.

Your open rates will plummet, your spam complaints will increase, and your likelihood of being blocklisted skyrockets.

Many ESPs prohibit sending to email lists that are not opted-in, and will offboard you if you’re found sending to one. And you will be found.

Also, it’s against the law.

But that didn’t stop 17.4% of brands from using one. On top of that, 9.5% of brands used a rented list.

Don’t. Purchase. Email. Lists.

Bad email collection processes

Landing on an email blocklist is almost always because of email collection processes.

Just because you don’t buy contacts, doesn’t mean that you’re in the clear.

The most common sources of email contacts are website and mobile app forms. Other sources include:

  • Live events
  • Webinars
  • Social media pages
  • eBooks
  • Contests

Signup forms and lead collection at live events are way more popular – and effective – than buying or renting lists (Source)

What does your email verification process look like?

An email verification process confirms that the email address you’ve collected from your contacts is their actual email address.

When your new contact fills out a form on your website or at an event this qualifies as a single opt-in. They have given their electronic consent to receive emails from you.

Typos, misspellings, or a junk email address are all still on the table. You have a couple of options:

  • Take their word for it that the email address is correct
  • Verify the email address

Email verification is commonly done using a double opt-in. A double opt-in adds an extra step in the form of a confirmation email.

  • Once your contact submits a form, a confirmation email is sent to their email address
  • Once they receive and verify that it’s real, you’re good to go

Verify your email address, so I know it’s real.

Search Engine Journal sends a great confirmation email (and also great content about SEO and other marketing-related things).

Do you monitor engagement and deliverability?

20.7% of brands don’t. To make things worse, only 45% of brands remove chronically inactive users.

If you want to take a step away from the blocklists, practice email list hygiene. Create a sunsetting policy.

A sunsetting policy is way to say that you’re not going to send emails to unengaged contacts after a given amount of time. It’s up to you to decide how long you keep unengaged contacts around, but a good starting point is 60 days.

How do you get off an email blocklist?

It’s a common misconception that landing on a blocklist is the end of the road for you. It’s not.

Being blocklisted is serious, but it’s usually pretty easy to get delisted. Delisting happens in a few different ways:

  • Your ESP will let you know and help you get delisted
  • Most blocklists will tell you what you need to do to get removed – this is called a “blocklist removal process”
  • Some blocklists are automated, and you’ll be removed once the criteria that landed you there is changed
  • You must remove the spam traps from your list and stop sending emails to them

Each blocklist has its own criteria for identifying IP addresses as an offender and removing offenders from their lists.

There are two types of blocklist removal processes:

  • Self-service removal – go to the blocklist site and follow their instructions for how to remove your IP. Make sure that you have resolved all the issues on your end before going forward.
  • Time-based removal – resolve the issues on your end (spam traps, purchased lists, spammy language in emails) and wait for the list to refresh. This usually happens within a week or two for light offenders, and longer for high volume or multiple offenders.

Once you’re delisted, stay delisted. If you land on the blocklist again (re-listed) it will take even longer for you to be removed. Blocklists keep track of who has been an offender in the past.

How do you stay off email blocklists?

There are 3 things to practice that will ensure that you don’t land on an email blocklist.

  1. Engagement clean-up
  2. Check your emails for spammy language
  3. Don’t purchase, rent, or scrape email lists

What is engagement clean-up?

Engagement clean-up means you’re paying attention to your list. It is central to practicing good email list hygiene. You see which contacts are engaged, and which are not.

Engagement clean-up includes sunsetting policy and removing contacts that just aren’t that into you. Engagement clean-up also includes a re-engagement email campaign. A re-engagement email campaign is a final attempt to bring your contact back in before removing them.

In ActiveCampaign, you can automate the process of engagement clean-up with our engagement tagging automations. Our platform will tag your contacts based on their level of engagement with your emails. You can even automate the re-engagement process.

You can get this exact automation imported into your ActiveCampaign account through this link!

Once tagged, you can use the ActiveCampaign list clean-up tool to remove any contacts that have been unengaged within a given time period.

“If you set up the engagement tagging automations, you will never set off or get on a blocklist.” – Alex Grim, Deliverability Specialist

Get rid of spammy language in your emails

The actual language of your emails is important. Email clients like Gmail, Yahoo, Microsoft, and others scan the copy of emails and make a decision based on what they see.

Avoid:

  • Heavy sales language
  • References to “free” stuff
  • A lot of links
  • Sleazy money phrases

If you’re using ActiveCampaign, every campaign and automation email you create will be scanned with our spam check tool. This tool flags anything that would set off an email client’s spam alarm, so your emails land in the inbox and not the spam or promotions tab.

Don’t purchase, rent, or scrape email lists

Purchasing, renting, or scraping an email list is a surefire way to get blocklisted.

It’s also a great way to get removed from email marketing platforms, ruin your deliverability, destroy your sending reputation, and break the law.

With new data security laws like the GDPR, purchasing an email list can get you in serious trouble including large fines and even jail time.

Conclusion: How to avoid email blocklists

If you’ve been on an email blocklist, it’s not the end of the world. If you practice good email list hygiene, you’ll be delisted in no time.

What’s important is to follow the best practices for email collection, verification, sending, and list clean-up.

If you put good policies in place, send emails to people who want them, and pay attention to engagement, email blocklists shouldn’t be an issue.