What is an Email Blacklist and How Do You Prevent Getting On It? Find Out Here

With all of the effort that you put into an email campaign, it’s unfortunate to realize that some emails never ever reach the inbox, effectively invalidating all your hard work. 

This can happen for a myriad of reasons – perhaps you’ve made a spelling error or entered an invalid email, which is no big deal. But there’s another reason why this could happen (a much scarier one) – you’ve been blacklisted.

Being placed on a blacklist is a serious matter. However, most marketers are not really familiar with this term and what it entails. If you’re one of them, I’ve prepared a complete guide to help you in this situation. 

So, what is an email blacklist and how can you avoid getting on it? Read on to find out!

What is an email blacklist?

A picture that shows the mail app icon.

A blacklist is a live list of IP addresses or domains that have been identified as spam senders

Companies, including Internet service providers (ISPs), free mailbox providers, and anti-spam suppliers use these blacklists to keep spam out of their systems.

Depending on the volume and quality of email and lists sent to, a person or ESP’s IP or domain can end up on one or more blacklists.

While having your perfectly crafted emails rejected before they ever reach your subscribers may seem inconvenient, blacklists are actually incredibly useful. They exist to keep a vast volume of unwanted emails out of people’s inboxes, as about 85% of emails received every day are deemed spam. 

Although some big ISPs have their own internal blacklists, many others rely on publicly available blacklists maintained by organizations that specialize in this area.

3 Types of email blacklists

Here are the three most common forms of email blacklists to be aware of:

  1. Public blacklists

This is the type of blacklist that is made public. This means you can check it yourself using email blacklist checker programs that monitor the top 100 publicly viewable blacklists on the internet.

  1. Enterprise SPAM firewalls

This is essentially a subset of publicly available blacklists. SPAM firewalls in certain corporate IT departments keep it up to date. McAfee, Cisco’s Ironport, and Barracuda are some examples.

  1. Private/ISP blacklists

Internal blacklists are common among large ISPs. Some companies let you see whether you’re on their blacklist, while others don’t.

Email services like Gmail, for example, have their own internal blacklists as part of their spam filtering technology.

This implies you can’t check if you’re on their list directly. You can only tell whether you’re doing it by looking at your email server logs.

How to find out if your company is on an email blacklist

Are you wondering “How do I know if my email is blacklisted?” 

Using a publicly available tool is the quickest and easiest way to check. These are some examples of DNS lookup databases:

  • MX Toolbox
  • DNS Stuff
  • MultiRBL.Valli.org

You can perform an email blacklist check – your IP address will be checked against more than 120 publicly available blacklists using these free tools.

You should also monitor email marketing statistics, such as open and click rates. More importantly, keep an eye on domain openings on a regular basis. If you see a significant decline in domain openings, it’s likely that you’ve been banned by an ISP.

How companies get on blacklists

While being on a blacklist can appear to be highly technical or even random, it is neither. These are some of the factors that might lead to blacklisting:

  • Spam complaints

When recipients of your email click the Spam button, ISPs assume your email content or list hygiene is poor. The more complaints an IP receives, the more probable it is to get blacklisted.

  • Lists of incorrect addresses

Bounced email addresses indicate to ISPs that your list isn’t opted in or up to date. 

Spamtrap addresses are used by several blacklists to identify spammers. A spam trap is an email address that isn’t used by anybody but can be publicly discovered and collected for lists. Any emails sent to it will not come from opted-in lists, but rather from outdated or bought lists.

  • An increase in the number of people on the list

As new customers or leads join up to receive emails, your email marketing list will increase over time. Most ISPs (and email service providers) will believe a list has been bought if the size of it increases dramatically in a short period of time, which can lead to getting blacklisted.

What to do if you’re on a blacklist

The first step is to remain calm. There are hundreds of blacklists throughout the world, and your IP address is likely to be on at least one of them. For the most part, this won’t have a significant influence on your capacity to communicate with your consumers. 

If you’re on a blacklist, it might mean that something is wrong with your email marketing. ISPs’ usage of larger lists can have a greater influence on the delivery of your emails and, as a result, on your business.

If your IP address is identified and placed on a blacklist, you must contact the list to request that it be removed. Each of the main blacklist firms has information on how to be removed from their databases on their websites. 

Typically, the process is quick and uncomplicated; simply follow their instructions to clear up your emails and lists. If you continue to mail smaller lists and do not receive a lot of spam complaints, the IP address should slip down on its own. 

If you’re using an email service provider, they’ll tell you what you need to do to repair the problem with your email and lists. 

How to avoid getting blacklisted

A photo showing a segment of the Gmail user interface.

To avoid going through the email blacklist removal process, the best thing to do is to actually prevent ever getting on it in the first place. 

Here’s how to avoid being placed on any blacklists:

  • Maintain a well-curated email list

Email lists containing invalid addresses are the most common cause of email blacklisting. Never buy a mailing list since the addresses are almost certainly fake. 

In the worst-case scenario, certain addresses are spam traps, practically guaranteeing your inclusion on a blacklist.

Here are some ideas for cleaning up your to-do list:

  • Remove any email addresses that have bounced. You don’t want to delete addresses that are suffering a momentary blip, so be careful to distinguish between hard and soft bounces.
  • Examine the statistics on performance. Delete outdated addresses that have a poor track record, such as low open rates.
  • Honor client requests to be removed from your email subscriber list.
  • Use double opt-in for email subscribers

A two-step email verification method is known as a double opt-in. 

In the first step, the user subscribes to the website’s mailing list. The user will receive an email with a link to confirm their email subscription in the second step.

Double opt-in techniques help to prevent email fraud by ensuring that receivers are actual humans who want to receive your marketing communications.

  • Protect your server

It’s critical to ensure that your server is free of viruses and bots

These malicious apps use your email domain or IP address to send fraudulent emails, so even if you haven’t done anything illegal, you may find yourself on an email blacklist. This malware has the potential to infect your server without your awareness, therefore keep your server security up to date.

  • Watch your email content

There’s a chance you will receive spam complaints if you send blanket emails to everyone on your list.

An image that shows a person sending blanket emails.

Personalize your emails and content to ensure you’re providing what your subscribers anticipate from you and to keep the information interesting for them. 

Keep in mind how often you send emails in addition to the content. If you send to huge lists or increase the frequency of your emails, you may experience delivery issues.


Being blacklisted can seriously harm your business, which is why it’s critical to keep track and know if and when this happens to you. 

As it always is, prevention is the best cure in this scenario too, so try to do your best to prevent getting blacklisted. If it still happens, now you know how to act and what to do to get back on track.