Blacklisted Email: How To Protect Your Emails From Ending Up on a Blacklist

Knowing more about email blacklisting will keep your emails away from being blocked.

Gracija Atanasovska

Content Writer

Even with email automation, crafting and sending email campaigns is not always an easy or straightforward process. Not only do you have to create a decent body of text and include relevant content, but it’s also important to get the email subject line right, include attractive visuals and CTAs, and segment your audience, among other things.

Did you know that, as measured in 2020, “20.4% of all emails either go to spam or remain undelivered” which is actually “an increase from 16.3% in July 2019.”

Email campaigns are hard work and it’s a real pity that some emails actually end up being blacklisted into spam and don’t even make it to the inbox section of your customers/subscribers.

And you definitely don’t want your email to be blacklisted, which is why you’re here. It’s not the end of the world, but it’s serious business, and a lot of marketers out there don’t understand it fully.

If you use a good, high-quality email service provider (ESP), then there’s a good chance your emails won’t end up being blacklisted. Nevertheless, it’s always a good idea to know more about this process in order to prevent it from ever happening or to know what to do if it ever does happen.

Let’s go over some of the basic stuff about blacklisted emails, after which we’ll show you how you can avoid it.

What Is an Email Blacklist?

Email blacklisting is when an email address is being identified as a spam and the content of those messages is being blocked.

A blacklist is actually a real-time list that’s used by internet service providers (ISPs), anti-spam vendors, and free mailbox providers, all with the intention to prevent spam from reaching their users’ inboxes. Email blacklists can be hosted and updated by email marketing companies, or other types of software and marketing companies, which can also join forces with companies that specialize in the field of creating email blacklists for various businesses.

The IP or domain of the emails sent can be found on more than one blacklist, depending on the amount of emails, as well as the quality of those emails.

The IP information is kept on a list that’s stored on email servers which then block the emails sent from the blacklisted IP addresses. This is what keeps email marked as spam outside of people’s regular inboxes.

Email blacklisting has to happen one way or another. It’s a way of keeping some kind of order in the world of more than 300 billion emails being sent daily.
In fact, only a small portion from those emails are actually considered legitimate - 15.61%, to be more precise. The rest, which is an estimated 84.39%, are discarded into the spam category.

A problem arises when emails that aren’t really spam are unfairly categorized as such. This happens when the blacklisting software fails to distinguish good emails from bad ones.

How Does Email Blacklisting Work?

When you send an email, it always contains an IP address, which is basically a line of digits, that tells the server where the email came from. You can look at it as the return address on regular letters that you send and receive from the post. The way to trace the email location is by its IP address.

So, when an internet service provider (ISP) receives a particular email, it also automatically looks up what its IP address is and checks whether it’s on any blacklist. If the IP address is on a blacklist, the email is considered spam and the software prevents it from ending up in the inbox. If, however, it isn’t on the list, it will go through some more spam filters before it lands in your customers’ inboxes. The other spam filters vary depending on what kind of ISP you’re using. So, yes, as you can see, the blacklist isn’t the only tool that decides whether your email will end up as spam or not.

It’s the ISPs’ job to identify IP addresses that are responsible for sending spam emails. So, usually, these ISPs identify IP addresses according to whether or not they have a history of sending such emails. If the IP address sends good emails, then they won’t end up in the spam folder. However, if the IP address repeatedly sends irrelevant or unsolicited email messages that are considered spam, or if it sends a spam trap email even once, it will end on the blacklist.

What Are the Main Types of Email Blacklists?

Email blacklists come in three main types:

  • Enterprise spam filter or enterprise spam firewalls - these are usually used by big companies and IT corporations and businesses. Barracuda and McAfee are some of the most famous examples of such softwares and programs.
  • Private blacklists - these are part of the internet service providers (ISPs). Take for example Gmail, which has its own registry of blacklists that it uses to filter potential spam emails.
  • Public blacklists - these are available online and can be checked by anyone, for free.

What Does It Mean When Your Emails Are Being Blacklisted?

When your email is blacklisted, it means that it won’t arrive at the intended address. This is bad for several reasons: it can cause revenue loss, it can subvert the effort you put into your marketing campaign, and it can make you lose face in front of your customers.

What’s more, the ISPs don’t need to tell you why an IP address has been blacklisted, nor do they have any obligation to fix the problem or hear your complaints.

Another thing that sometimes happens with email blacklisting is that sometimes it’s not your IP address that will get blacklisted, but the particular domain from which the email was sent, though this is basically the same thing as IP address blacklisting.

How Does an Email End Up Being Blacklisted?

Unfortunately, it’s not always the case that only bad emails end up on the email blacklist. Sometimes other factors contribute to your emails ending up being listed as spam, rather than finding their place in your customers’ inboxes.

Sometimes, a swarm of spam complaints, to an otherwise good email, or just a faulty email list, may contribute to getting your email blacklisted.

So, let’s go over the most important reasons why your email messages may end up being blacklisted as spam.

Email List That Hasn’t Been Revised

Email list hygiene is an important part of the process of keeping your emails away from being blacklisted.

If your email list contains plenty of inactive addresses or inactive inboxes whose sole purpose is to be spam traps, then your sender reputation is likely to get spoiled. Harvested emails that have been used as spam traps are also used by ISPs to locate bad email addresses. And, if your email address ends up in some of these inboxes, then the provider might also consider your email as spam.

You’ve Been Attacked By Hackers

Hacker attacks may be another reason why your email ended up being blacklisted. Perhaps they’ve somehow gotten hold of your account, and are sending spam emails. Or, they’ve been mimicking your email address and using your IP address to send fraudulent and false emails to people.

How can you know this is happening? Well, one indication is when you get lots of error messages for emails that you actually haven’t sent. This means that your account might’ve been compromised.

You Send a Lot of Emails (High Emails Volume)

Remember the statistic I mentioned earlier, that 84% of emails out there are considered spam?

If there’s a significantly higher volume of emails sent from your IP address compared to other IP addresses out there, this might indicate that your account is sending spam mail.

Yeah, so the logic here goes: if you send too many emails from an IP address, you might be a spammer. The higher the volume of emails coming from one IP address, the likelier the chances for those emails to be blacklisted.

Increased Email Traffic

Similar to high email volume, increased email traffic can also make ISPs think that you’re a spammer. If, for example, you experience a sudden spike in email traffic and sudden enlargement of your email list, then the ISP can mistake this for a suspicious spamming attempt.

That’s because there’s a general opinion that professional organizations work on their email lists slowly and gradually, over a longer period of time.

Complaints About Spam

When a user receives an email in their inbox, they usually have the option to mark it as spam if they consider it as such. And even if there’s nothing wrong with your email, this can sometimes occur. It happens to everyone and, in general, it’s nothing to worry about.

However, when these complaints become too frequent, it will catch the attention of the ISP, and your emails may end up being blacklisted, after all.

Bad, Misleading, or Irrelevant Email Content

Some ISPs contain filters that filter emails according to keywords and other elements that are present in the body of the email text.

So, stuff like using caps lock, too many emojis and exclamation marks, too much interpunction, as well as words like “free” or “guarantee money back” can all be considered parts of an email that needs to be blacklisted as spam.

Poorly Managed Email List

This is similar to the first reason I mentioned on bad email list maintenance.

If you don’t take good care of your email list and don’t allow people to unsubscribe if they’ve requested to do so, then your emails might be reported as spam, and voila - you’ve ended up being blacklisted by ISPs and other security software and programs.

ESPs (email service providers) are usually able to take care of ISPs’ blocks and blacklistings on their own. But, if your own email is actually at fault, this is not going to be so easy.

So, How Many Emails Can You Actually Send Without Being Blacklisted?

It’s not just that a high amount of emails and email traffic, as well as a sudden volume spike, will get you to the blacklist.

I mean, big corporations are sending a huge amount of emails every single day, and they’re not getting blacklisted or considered spam. But this, of course, is because they’ve built their email list over time, and abide by certain common email ethics.

But, if all of a sudden you start sending thousands of emails per day when yesterday or last week you’ve been sending much less, then it’s quite likely that it’ll catch the attention of the ISPs and that your company’s IP address will end up being blacklisted, or at least suspicious of sending spam.

Email lists and email volumes have to increase naturally (organically) so you don’t become a target of spam filters and blacklists.

What Can You Do if You Have Been Blacklisted?

Unfortunately, sometimes you’ll do all the right things and still end up being blacklisted. Even successful email marketing campaigns can get blacklisted, and it doesn’t mean that it’s the end of your campaign or your business.

If it ever happens, don’t worry. It’s not as scary as it sounds and it’s fixable.

The good news is that most of the blacklisting companies have their own ways to appeal your blacklisted status and to remove the IP address from that infamous list. You will need to contact the blacklisting company and get familiarized with the steps you’ll need to take to get off that list. It’s a fairly simple process, you just have to follow their instructions, clean up your email lists a bit (if necessary), and you’re done.

Also, sometimes it’s possible that a blacklisting company removes your IP address from its list when the complaints for it decrease or stop coming altogether.

If you’re using an email service provider (ESP), then it’s usually up to them to fix the problem. They will contact the blacklisting companies and request your IP address to be removed from their list. However, you will still need to fulfill some demands from the blacklisting company (if they have any) before they unblock your address.

How to Avoid Becoming Blacklisted

The best solution is to avoid getting blacklisted at all (if possible). So, if you don’t want to end up on a blacklist, try to avoid the stuff that’ll make you get there in the first place. Here are some ideas.

Keep Your Email List In Check

Poorly maintained email lists are arguably the first reason why you may end up on an email blacklist.

Make sure to keep your lists clean from any bounced or old email addresses that don’t perform well, and addresses from which people have requested to unsubscribe. If you notice that some people on the list haven't opened your emails in a long time, don’t wait any longer and remove them from your email list.

Don’t Buy Any Email Lists That Are For Sale On the Internet

Nowadays, you can find plenty of sites which offer you to buy already assembled email lists. Sounds like an easy way out, right? In reality, though, it’s a really, really bad idea, especially if you want to avoid being blacklisted.

That’s because the majority of those email addresses simply aren’t legitimate. Best case scenario they’re stale, unusable email addresses, and worst case scenario - they’re spamtraps, which is an accident waiting to happen when it comes to email blacklists. Instead of boosting conversion rates and expanding your email marketing campaign, you’ll get more spam complaints than you’ve ever hoped for. Also, not to mention you’ll struggle with lots of delivery issues.

Use a Double Verification Process for Your Email Subscribers

For those of you who are unfamiliar with this term, double opt-in is a two-step email verification process. The first step includes the user signing up for your site’s mailing list, and the second step is the email which you send to the subscriber containing a link that the subscriber needs to click in order to confirm their subscription. This way, only when the user clicks the verification link will they be added to the email list.

These double opt-ins are a good way to counter email fraud, because they provide a way to ensure that the user who subscribes is actually a real person, and not an artificial bot.

Also, they’re good for ensuring that customers actually want to find themselves on an email list. They’ll be sending out complaints much less often this way.

Keep Your Server Protection Up to Date

Another way to ensure that your IP address won’t end up getting blacklisted is server protection.

You will have to make a thorough check up and see whether your server has been somehow compromised by bots or malware. These kinds of programs are able to hijack your IP address or the domain of your email and send all kinds of false emails. And that’s how they’ll get you to an email blacklist even though, from all you know, you actually haven’t done anything wrong.

Bots and malware can enter your server when you least expect it, often without your knowledge, and that’s why it’s all the more important that you have all the security protocols updated and well-maintained.

Send Relevant and Personalized Email Content

Paying attention to your email content is an important part of your efforts to avoid the dreaded blacklist.

The content of your emails matters to your subscribers and it’s often the thing that’ll determine whether your email gets opened or not.

The body of your email should be able to keep users engaged and interested enough so they’ll open your emails every time they arrive. If you send emails that are too general to every person on your list, it’s likely that they’ll be reported as spam by some of your subscribers.

If you want to avoid that, keep your users engaged by sending timely, relevant, and personalized content that’ll correspond to what they want and need to know at the moment.

Keep an Eye on the Analytics

If you’re in the middle of an ongoing email campaign, I’m sure you’re already keeping track of the email open rates and click-through rates.

However, it’s also important that you track how much your domain is being opened as well. If you notice a sudden drop in domain opens, you should consider checking whether your IP address/domain has ended up on a blacklist.

Segment Your Email Lists

Segmenting your email subscribers will ensure that you always send them the most relevant content. Break up your email list into segments based on certain criteria, like demographics, current place of residence (country, city), their interests, buying habits, their history of past purchases or uses of your services, etc.

Email segmentation will help you craft better email content and it’ll ensure you send out the right messages to the right people, just when they need them the most.

Design Your Emails In a Way That You’ll Ensure Customer Engagement

The more your customers engage with your emails, the less spam complaints you’ll receive. Consequently, there’s a lesser of a chance you’ll end up on an email blacklist.

One of the best ways to do this is, again, to craft an email according to the wants and needs of your users, and curated after their own individual consumer histories and buying habits.

This is one of the best ways to have high open rates and low spam reports. Couple that with clean email lists and proper email segmentation, as well as high deliverability, and you’ll keep your customers happy and engaged with your content and your business. What’s more, you won’t have to worry about any blacklisting in the near future.

Final Thoughts

As you can see, email blacklisting is not a walk in the park, but it’s not a death sentence either. That’s not to say that it shouldn’t be taken seriously, though.

Even the best email campaigns may end up being blacklisted. Even if you do everything right, sometimes it can be sheer bad luck and the next thing you know you’re writing to blacklisting companies to straighten the injustice.

But sometimes it can also be your own fault, which means you’ll have to do some tidying up when it comes to your email lists as well as your server(s).

Make sure you track all the relevant email marketing statistics, and don’t forget to check the domain opens alongside the open and click-through rates. A sudden sharp drop in domain opens can be a good indication whether your IP address has been blacklisted from an ISP or not. If you have a good ESP, they’ll do a good job taking care of it.

Other times, though, you won’t as easily notice that you’ve been blacklisted. That’s why it’s so important to follow our advice and do what you can to prevent this. Prevention is the best medicine and using good email tactics like slow contact building and server and email list maintenance, along with proper segmentation, will keep you away from becoming blacklisted.

That being said, before I end this article, I want to give you a few public links where you quickly check whether your IP address or domain is currently blacklisted.

These are some of the more common tools that are publicly available to all databases on the internet, which can check up to 120 openly available blacklists:


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