What is an Email Blacklist?

Around 45.37% of global email traffic is classified as spam. Unfortunately, legitimate marketing emails can sometimes be blacklisted, contributing to this figure and harming deliverability.

Sometimes, we take for granted what our email deliverability pros know versus what brands and our customers know. Since our clients come from all sorts of backgrounds, it’s essential to ensure everyone’s on the same page. That’s why understanding what email blacklists are and how they affect both your email deliverability and overall email marketing performance.

Many clients ask about blacklists—what they are and why they matter. In this blog, we will dig deeper into blacklists and blocklists, how they’re connected with spam traps, and what you can do if you find yourself on one.

What is an Email Blacklist (Blocklist)?

An email blacklist, or blocklist, is a real-time database that tracks IP addresses or domains flagged for sending spam or malicious content. ISPs, mailbox providers, and anti-spam tools use these lists to block unwanted emails. Being listed can severely impact your email deliverability, preventing your messages from landing in inboxes.

The terms “blacklist” and “blocklist” are often used interchangeably. They both refer to a list of IP addresses, domains, or email addresses flagged as spammy or malicious. These lists can be public or private, and getting listed on one can significantly hurt your email deliverability, especially if major email service providers (ESPs) use the list for filtering.

Whether you’re sending bulk emails through an ESP or individually, your sending reputation can be affected by both the quantity and quality of the emails you distribute.

So how does all this work?

Picture This: Your IP or Domain is Flagged As a Spammer

Suddenly your email campaigns stop reaching your subscribers. Scary, right? That’s what happens when you end up on a blacklist. But don’t worry—it’s fixable, and it starts by understanding how you got there.

While there are many different types of blacklists, at the root of most blacklists are spam traps—email addresses specifically created to catch and identify spammers. There are millions of spam traps and several spam trap networks that exist, and one of the things these spam trap networks do is “publish” their findings as listings. These listings make up the “blacklist” or “blocklist”. Depending on the spam trap network, these listings could be private or they could be public. So, if you hit one of these traps, the network might add your IP or domain to a blacklist.

The Impact of Being Blacklisted

If your first thought of an email blacklist is being shunned, you’re right – in the email sense.

When your IP or domain lands on a blacklist, it can seriously damage your email marketing performance and prevent your messages from reaching your audience. Many ESPs and ISPs reference these lists to filter out spam, which means your emails may never reach your subscribers’ inboxes, having a catastrophic impact on your deliverability to almost being non-existent.

If you get listed on a major list, your open and click-through rates could plummet, and your team will likely start scrambling for answers. But if you hit a smaller, less-referenced blacklist, you might not notice an immediate impact.

Even if you’re flagged on a minor blocklist, and everything seems fine, it’s important to address the root issue. Without doing this, that small listing could escalate, catching the attention of larger blacklists. This makes it increasingly difficult to get removed and can seriously harm your sender reputation.

At this point, many mailbox providers, ISP’s and corporate systems usually reference some sort of blacklisting service as a part of their email filtering process. The tricky part is not everyone references the same lists, and they won’t disclose who uses what.

How to Get Off a Blacklist

Being blacklisted isn’t the end of the road. You can recover, but you’ll need to take action:

1. Identify the Source: First, figure out what caused the problem. Was it outdated email lists? Poor opt-in processes? Dig into your data and pinpoint the issue.
2. Clean It Up: Once you’ve found the problem, fix it. Update your list hygiene, remove any questionable data, and ensure the mistake doesn’t happen again.
3. Request Removal: Reach out to the blocklist provider and explain what went wrong and how you’ve resolved the issue. Be as detailed and cooperative as possible to increase your chances of a speedy delisting.

If all goes well, you’ll be removed from the blocklist, and your deliverability should improve. But remember: Repeated issues can make it harder to get delisted in the future, with some providers imposing waiting periods, such as 30 days, before you can request removal again.

How to Avoid Getting Blacklisted

Prevention is always better than cure. Here are three proven strategies to help you avoid blacklists:

1. Use Double Opt-In: Make sure your subscribers truly want to hear from you by using a double opt-in process. This helps ensure high-quality engagement and fewer spam complaints.
2. Simplify Unsubscribes: Make it easy for people to opt out if they’re no longer interested. Hiding or complicating the unsubscribe process increases your risk of being reported as spam.
3. Regularly Clean Your List: Remove inactive contacts from your email list on a regular basis. Continuing to send to disengaged recipients can trigger spam traps and hurt your deliverability.

That’s the gist of email blacklists and how they work in conjunction with spam trap networks. While not all of them operate this way, a large number do!

The Importance of List Hygiene

Landing on a blacklist is more than just an inconvenience—it’s a critical reminder of why email marketing best practices matter. List hygiene, segmentation, and respecting your subscribers’ preferences aren’t optional; they’re essential to maintaining your deliverability and keeping your email marketing strategy effective.

So, next time you’re reviewing your campaign metrics, remember to take a close look at your list health and deliverability. A little extra attention to these details can go a long way in keeping you off those dreaded blacklists—and ensuring your emails land where they belong: in your audience’s inbox.