Demystifying blocklists

Deliverability Podcasts
In this Article

In episode 9 of the Deliverability Defined podcast, my co-host Melissa Lambert and I discuss blocklists and how to recognize if you’re being impacted by them.

What is a blocklist?

A blocklist is an organization that compiles a list of IPs and domains they believe to be risky. If a mailbox provider, spam filter, or mail administrator decides to use a particular blocklist, they can deny messages that come from an IP or domain that is listed on the blocklist.

There are hundreds of blocklists in existence, and each mailbox provider or spam filter has their own settings to determine which blocklists they pay attention to.

Typical reasons for getting blocklisted

IPs and domains are typically added to blocklists for hitting too many spam traps, or getting too many spam complaints. We have an episode on spam traps if you want to learn more!

Most senders are using an Email Service Provider (ESP) like ConvertKit to send mail which can make blocklists confusing.

  • If your domain is blocklisted, your email traffic caused the block.
  • If you're using a dedicated IP and the IP gets blocklisted, your email traffic caused the block.
  • However, if you're sending from a shared IP pool, any sender on the shared pool could have caused the IP to be blocked.

Lean on your ESP for help

In that last scenario, lean on your ESP!

Any reputable ESP, like ConvertKit, should have a deliverability and compliance team that monitors blocklists around the clock. They also monitor email delivery rates and are experts at knowing:

  • Which blocklists impact their customers
  • Who to reach out to
  • How to handle the customer who caused it
  • and more.

If your ESP has these proper procedures in place, you can rest assured that they will handle any impactful blocklists for you on the backend. Don't be afraid to ask your ESP about their processes if you're concerned.

How to get removed from a blocklist

Each blocklist has very individualized delisting processes.

  • Some blocklists automatically delist you after 24 hours
  • Some delist you after they see a decrease in spam trap hits or complaints
  • Some require you fill out a form for automatic delisting
  • Some require a very manual process where you need to reach out to them.

If you're using an ESP and their IP or domain is blocklisted, do not attempt to delist yourself. Again, lean on your ESP.

Deliverability and compliance experts at the ESP should be the ones to submit delisting requests as they understand how the blocklists like to receive these, what information they need, and there's often an existing relationship there.

How to tell if a blocklist is impacting you

Blocklists are a common cause of concern after using blocklist lookup tools or mailbox placement tools and seeing that your domain or IP is blocklisted. First, don't panic! The best way to know if your mail is being impacted by a blocklist is by looking at your bounce rates.

For most cases, being on a blocklist used by your subscribers will cause your messages to bounce. Therefore, a large number of bounces could be a sign that you're on an impactful blocklist.

However, if a lookup tool tells you you're on a blocklist but your bounce rate is < 2% — it's unlikely this blocklist is being used by your subscribers.

Blocklists can be specific! For example, there are blocklists for specific regions, such as Brazil. If you don't have customers or subscribers in Brazil, it's unlikely that a Brazilian blocklist would have any impact on your mail.

Some blocklists are more commonly used for B2C addresses like Gmail, Hotmail, Yahoo, etc., while others are more commonly used for B2B addresses. Spamhaus seems to be the most impactful blocklist across the board.

How to fix the root issues that cause blocklistings

1. Audit your list and make sure every subscriber opted-in to receive your emails/
2. Send an Opt-in confirmation email to anyone who hasn't opened an email from you in 12 months (potentially shorter depending on your situation). Remove subscribers who do not confirm their opt-in.
3. Ensure your forms are implementing double opt-in.


If you see you're on a blocklist, don't panic! First make sure it's actually impacting your mail. If it is, and you're using an ESP, lean on the experts at the ESP to handle the blocklisting for you. If you caused the block, they'll also know how to help you fix your root issue.

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Alyssa Dulin

Alyssa is a Deliverability Lead located in Nashville, TN. She loves helping senders reach the inbox of their subscribers. Outside of work, Alyssa enjoys traveling, indoor cycling, and spending time with family.

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