What is an email blacklist? And how to avoid ending up on one

The email blacklist is the nightmare of any email marketer.

Whether you’re doing sales outreach or running an email newsletter, you’ll want to steer clear of them.

We’ll show you what email blacklists are and how to avoid getting blacklisted.

Let’s dive in:

What are email blacklists? 🚫

Email blacklists are lists of domains or IPs of suspected spammers.

They allow email service providers(ESPs) to protect users from spam and other cybercrimes.

If your domain (or IP) is blacklisted, it means you’re being marked as a spammer.

Understandably, email service providers don’t like spammers. Spam is a nuisance at best and a serious security threat at worst.

Every time an email comes in, ESPs query blacklists using the sender’s IP address and domain (in some cases, even the exact email address).

If a sender is on a blacklist, their emails might get flagged, delayed, or blocked altogether.

The cost of being on a blacklist 💰

If you’re on a blacklist, your sender reputation will suffer.

ESPs keep a score on your sender reputation. If you don’t follow email deliverability best practices, they will lower it and potentially put your domain or IP on a blacklist. Usually, this happens after receiving too many spam complaints from recipients.

When ESPs put you on a blacklist, you will experience serious deliverability problems.

Just imagine the damage that can do to your ROI.

You can have the best cold email campaign ever, but it's worthless if it doesn't reach your prospects.

Why email blacklists exist 🛡️

In 2023, more than 45% of all emails sent were spam.

It’s a huge improvement from 2011, when it was 80%(!) of all email traffic.

Email blacklists have helped fight spam.

Now, when you’re on an email blacklist, you obviously “hate” them.

But the truth is: email blacklists exist to make email more secure and pleasant for everyone, reducing spam and keeping inboxes clean.

Without email blacklists, inboxes would overflow with spam, phishing, and other harmful messages.

Email blacklists protect email as a channel and, therefore, make it possible that email marketing even exists.

Types of email blacklists 📋

There are two types of email blacklists:

• Domain-based blacklists: If your sending domain shows a lot of spam activity and other suspicious behavior, it’ll likely end up on a domain-based blacklist. Any email sent from a blacklisted domain may get blocked or sent to the spam folder.
• IP-based blacklists: IP addresses of spammers may get added to IP-based blacklists. Any email sent from these IP addresses may get blocked or sent to spam the folder.

💡 Even an individual email address can get blacklisted, but it’s much less common than IPs and domains.

How do email blacklists work? ⚙️

As touched upon earlier, email service providers check if sending domains or IPs are on blacklists.

These blacklist queries happen in real-time during an SMTP connection.

If the sending domain or IP is indeed on a blacklist, the email is typically rejected or flagged.

But do you actually get on a blacklist?

Let’s discuss that now:

Best practices to avoid getting blacklisted ✅

Getting removed from an email blacklist is possible but not easy.

It’s much better to avoid getting on a blacklist in the first place.

Here are some of the best practices to avoid the dreaded email blacklists:

• [ ]  ➡️ Send high-quality emails: Sending cookie-cutter emails can increase spam complaints. Instead, make the emails about your recipients by personalizing them. When done right, recipients will actually like to receive your emails. Use a tool like lemlist to personalize emails at scale.
• [ ]  ➡️ Warm up your email: For new sending domains and those with a bad sender reputation, you must warm up your email or risk ending up on a blacklist. Starting with a low volume of daily emails can slowly build up a solid sender reputation and improve your deliverability, ultimately leading to higher engagement and more revenue. Use an email deliverability booster like lemwarm to help you with this.
• [ ]  ➡️ Use high-quality contact data: Poor-quality emails lead to high bounce rates, potentially triggering email blacklists. What’s more, you risk sending to spam traps. Spam traps are email addresses deliberately distributed to catch spammers. If you send to a spam trap email, you’ll be flagged as a potential spammer. To combat this, use high-quality leads databases, like lemlist’s People database and make sure to verify every email before using them.
• [ ]  ➡️ Reduce bounces: Excessive bounces (emails coming back after not getting delivered) can lead to being blacklisted. Email service providers track bounce rates, and if you’re experiencing bounce rates of 5% and up, you risk getting blacklisted. Here’s how to reduce your bounce rate.
• [ ]  ➡️ Avoid buying email lists: Many email lists that are up for sale are of low quality. Unverified or dated email addresses will cause bounces, low engagement, lost resources and revenue, and potentially land you on a blacklist.
• [ ]  ➡️ Use double opt-in for email lists: Doing conventional email marketing like email newsletters? Make sure to use double opt-in so that only the owners of an email address can sign up for your list. Single opt-in allows anyone to add any email address to your email list. When this happens, and the actual owner (who never signed up) gets your emails, they will quickly hit the spam button.
• [ ]  ➡️ Complete your technical setup: Your technical setup proves that you are the owner of your email-sending domain. By setting up the email authentication protocols like SPF, DKIM, and DMARC in your DNS domain setting, email service providers put more trust in your emails, making it less likely you get blacklisted. As an added benefit, your emails get better inbox placement.
• [ ]  ➡️ Add an unsubscribe link to every email: What do recipients do if they don't like your email but see no unsubscribe link? They click the spam button! A high spam rate is likely to land you on an email blacklist. Your spam rate should be under 0.1%.
• [ ]  ➡️ Avoid spam trigger words: Certain words and phrases like “free”, “cash bonus”, and “Prize” can trigger spam filters. Include too many of those, too many times, and you may end up on a blacklist. Here’s a list of 222 spam trigger words to look out for.

How to check if you’re already on a blacklist 🔍

Use our deliverability checker below to check if you’re on a blacklist.

The tool also checks if your technical setup is in order.

Double-edged sword ⚔️

Dealing with spam lists can be challenging.

You may sometimes wonder why they were invented in the first place.

However, they serve an essential role in keeping email secure. It helps to maintain email marketing as a viable promotional channel.

As long as you follow the best practices laid out in this post, you should keep yourself off any email blacklist.