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What Is an Email Blacklist and How to Avoid It: A Comprehensive Guide

Posted by Anastasia Kryzhanovska on December 4, 2020

What is an email blacklist and how to avoid it
Anastasia Kryzhanovska

Anastasia Kryzhanovska
Senior Content Manager

Anastasia is a content marketer and manager with a strong IT background, passionate about storytelling and SEO. She likes creating high-quality content and helping others develop their skills. Besides work, she loves traveling, extreme sports, and reading fantasy books.

Published on December 4, 2020

Considering the amount and the quality of work that typically goes into creating a stellar email campaign, it is undoubtedly disheartening when you learn that many intended recipients will never read your email. Indeed, a lot of good-intentioned companies land on email blacklists for various reasons that you’ll find later in the article.

On the one hand, these lists provide the user with some benefits, such as keeping their inboxes free of unwanted emails. But for a marketer, falling into an email blacklist is bad for business.

In this article, you’ll learn more about what an email blacklist entails and how to ensure your emails don’t end up in an email black hole.

What Is an Email Blacklist?

An email blacklist is a real-time database of IP addresses and domains used for deciding which emails should be considered spam. The IP address of the sender would be run through this database and is considered spam depending on preset criteria. 

You can think of it as a filter that determines whether or not an email makes it to its intended inbox destination. If your email or IP address is listed on one of these blacklists, it can affect your email deliverability, and your sales will likely take a downward dive.

Several email blacklist services provide these blacklists. Examples include Spamhaus, Invaluement, and SpamCop. They set up a special kind of algorithm that filters your mail out of the destination inboxes. So it’s either your email heads straight to the spam folder, or it’s never delivered at all. 

Why spam gets blacklisted

It’s important to understand that spam could mean different things to different people. Spam is broadly considered to be an unwanted or unsolicited email. Specifically, it can mean a malicious message intended to install harmful software, malware, or virus on your system. Usually, they come with a call to action, prompting you to do something that exposes your system to harm.

On the other hand, spam can be emails that you didn’t sign up for, yet you keep getting them. They are not harmful to your computer, but they constitute a nuisance in your inbox. Internet service providers (ISPs) and anti-spam vendors use spam filters or blacklists to prevent spam from getting into their system or reaching their network.

How blacklisting happens

Typically, when you send an email, an ISP receives it and checks it against a list of existing blacklists. The ISP runs your IP address or domain through the database. Depending on whether or not you’re on that database, your email is rejected or delivered to its destination inbox. 

Additionally, the rejection of an email is also determined by the policies of the ISPs. So, the blacklists are sometimes just one of the criteria used to decide if your email is bounced or labeled as spam. 

Most Commonly Used Email Blacklists

Email blacklists are so many these days that you hardly know which ones among them to actually worry about. In fact, there’s a high probability that your IP address is currently listed on one or more of them. However, you should not worry about all of them, as there are just very few that can impact your email deliverability.

Below are the major email blacklist services you should worry about. Essentially, the lists provided by these companies are used extensively by email service providers, internet service providers, and major businesses around the globe. You want to avoid getting on them, lest your email deliverability will plummet.

Spamhaus Block List (SBL)

Spamhaus comprises numerous lists used by many companies and ISPs. This includes SBL Spamhaus Block List, DBL Domain Block List, XBL Exploits Block List, and several others. You’re most likely to encounter SBL during your regular email marketing campaigns.

They also use spam traps to blacklist IP addresses that send out spam emails. A spam trap is an email address which no one uses. However, it might still be publicly found and harvested to build email lists.

Composite Blocking List (CBL)

Spamhaus also maintains the Composite Blocking List. However, the CBL only blacklists IPs known for malicious characters, such as spambots, open proxies, and dictionary attacks. If, for instance, your website is compromised by hackers, the website’s server becomes listed on CBL as soon as CBL picks up that server.

Spamcop

Spamcop uses spam trap addresses and spam reports to create a blacklist. Basically, they generate a reputation score for your email or website based on the number of spam reports against you. Your email address or website is added to the list after a certain number of complaints, in which case your reputation score must have dropped very low. However, to balance things out, the reputation score of your IP is often weighed against the spam reports.

Invaluement

Just like Spamhaus, Invaluement runs several lists, which could be domain-based, IP-based, or network-based. Examples include ivmURI, ivmSIP, and ivmSIP/24. ivmSIP is IP-based and lists IP addresses that have high spam reports. If your IP address features on this list, you will have serious problems sending out emails.

Barracuda

This is the blacklist system that powers Barracuda anti-spam appliances. IPs are listed on Barracuda blacklists when they send spam directly to Barracuda Reputation Detector. Also, if your server has been compromised, you’ll most likely find your IP address listed here.

SenderScore

SenderScore serves lots of organizations, including major email service providers (ESPs) and email marketing service providers. SenderScore is Return Path’s sender reputation system. With SenderScore, the lowest reputation score is 85, below which you’ll likely have email delivery issues. But while SenderScore will not block you directly, it sends your reputation score to spam identification systems. The systems, in turn, determine if your emails should be blocked or not.

Passive Spam Block List (PSBL)

PSBL is not as stringent as the other blacklist services. They rely simply on spam traps. If your server sends emails to PSBL spamtrap, that server’s IP address will be picked and blacklisted. However, you can easily get off their blacklist by requesting to be removed.

Exploits Block List (XBL)

XBL mainly blacklists compromised IP addresses, open proxies, botnets, and other spam engines. They keep a real-time database of hijacked servers too, and if anyone uses your server as a spam gateway, the IP address of that server will be flagged and listed on XBL. 

Reasons Why You Might Land On a Blacklist

If you rely very much on email marketing techniques to get your clients to take actions on your website or win new clients, you would want to guard against falling on the wrong side of these email blacklists.

It is very easy for an email to be blacklisted, considering many people cringe at the sight of too many messages hitting their inboxes every day. Therefore, the more users report your email as spam, the higher the odds are against you. Here are the reasons why an email address may be sent to a blacklist. 

High spam reports

The more complaints about your email being spammy, the more likely your IP address will be blacklisted. As much as you can, you want to avoid situations that lead your subscribers to click the spam button. It leads ISPs to think your email content is malicious or spammy. And despite how clean your mailing list can be, this is very much possible.

A sudden increase in your mailing list size

When there’s a surge in your mailing list by size, you risk being blacklisted. Ideally, your mailing list is supposed to grow gradually over a period of time as more and more people subscribe and sign up to receive your emails. But, if your list grows disproportionately with time, especially over a short period of time, ISPs and ESPs can flag it as an unhealthy purchase of emails.

You got your hands on a bad list of email addresses

When you send out emails and those emails bounce, it is not good for your reputation score. When you have a lot of bounced email addresses, ISPs see it as spam — either the users did not opt in themselves, or the list is not current. Remember that blacklist services such as Spamhaus and Spamcop use spam trap addresses to find spammers. So, you will not find such emails in opted-in lists; hence it only means that emails sent to it are spammy.

Email spoofing

This is a technique commonly used by spammers to deceive people into believing that an email came from someone they know or trust. Therefore, hackers forge the sender’s address in this case. Email blacklist services have algorithms that notice and flag such unhealthy use of emails. Well, it’s highly unlikely that you would want to launch a spoofing attack on your subscribers, as it is a tactic employed chiefly by spammers.

“Good old” hacking

When your server is hijacked, there’s a probability that it will be used to launch phishing attacks on your subscribers. This is perhaps the most common reason why legitimate emails are blacklisted. Once the hackers hijack your account, they use it to send large volumes of emails to your subscriber’s list. This leads to the next point.

A sudden increase in the number of outbound emails

If you normally send out two or three emails in a week, your email service provider will definitely suspect something funny when you begin sending out hundreds of emails in a week. This will most likely get you blacklisted. However, you can request removal from the email blacklist after contacting the owners of the blacklist and doing as instructed.

How to Avoid an Email Blacklist

Seeing how relatively easy it is to get blacklisted and the added damage it does to your email marketing campaigns, you want to try as much as possible to avoid getting listed. As we’ve seen, the primary causes are bad email lists and poor email content. Follow the suggestions below to ensure you stay off email blacklists. 

Don’t buy mailing lists

For your own good, you want to avoid buying mailing lists. Instead, work on building your own. The benefits of building your list are quite attractive, only that it takes time. For starters, you don’t have to pay anyone to keep your list. Secondly, they’re organically generated, meaning that your subscribers willingly signed up themselves. That’s a sign that your content is wanted, and it’s also a great way to build trust in your brand. 

But most importantly, you won’t need to worry about having anyone reporting your email as spam. If they decide to stop receiving your emails, they can easily unsubscribe from your emails. Additionally, you should remove bounced emails and emails that no one opens from your list.

Check your email campaign statistics

Checking your blacklist status from time to time is one of the best ways to ensure you’re in line. And if you ever get on any of the blacklists, you can know quickly and act on time. It’s often easier to keep an eye on the clicks and open, but you should watch your domain opens just as much. When you begin to get lower engagements over a while, you should check your email blacklist status. 

Work on improving your email content

Besides sticking to a naturally growing email list, the biggest game-changer when it comes to avoiding blacklists is churning out great content. While you improve your email content, also ensure to personalize your emails. Email personalization helps you get better engagement from your subscribers. If you send emails daily or weekly, be sure to keep your readers engaged with content on matters that interests them, but do not send too many at a time.

Segment your mailing list to improve your results

As your list grows, chances are you’ll have more people with different interests. The best way to serve them all is by segmenting them based on their locations, age, specific content. In order words, you can send to each subscriber precisely what they want to see.

Tips for Improving Your Email Content

Seeing how crucial content is, you should ensure to keep your subscribers treated continuously to interesting and neatly crafted content. Here are some tips you can try to achieve this. 

  • Use attention-grabbing subject lines: the reason most emails never get opened or even read is the subject line. If it’s not short, personalized, and engaging, chances are, your subscribers will read your emails less often, even though you have excellent deliverability and great content. 
  • Emphasize your CTA: Getting your emails opened is just scaling the first hurdle. They might still just skim over it and move on without taking any action. The ideal process flow is to get them to read a brief, straightforward copy in the body of the email, then cleverly introduce your CTA. Ensure the copy doesn’t sound generic or uninteresting. 
  • Make your content mobile-friendly: understandably, the majority of your email campaigns are created on a computer. However, you need to also factor in the reality that the majority of your subscribers will likely open their emails on mobile devices — phones most times. The results are better when users can enjoy the same experience on their mobile device as someone using a computer. 

What to Do If You Were Added to a Blacklist

If you send a lot of emails, the chances are that your email is listed on, at least, one of the email blacklists out there. But no need to panic. You can always get off a blacklist, so long as you follow the instructions provided by the owners of the blacklist. 

While you may not need to bother about the consequences of being on smaller blacklists, you definitely need to worry about appearing on bigger ones like Spamhaus, as it spells bad luck for your marketing team. Obviously, something is wrong with your email marketing campaigns, and you should correct it as soon as possible.  

In some cases, if you continue sending out clean, informative emails, the blacklisted IP address will likely drop off on its own. But, for the majority of cases, you need to reach out to the blacklist service and have your email address, domain name, or IP address removed.

Step 1: Identify which blacklist you’re on

You can use an email blacklist checker like MXToolbox to check if your IP address is blacklisted or not. MXToolBox is a blacklist checker you can use to check a mail server IP address against several DNS based email blacklists. Instead of checking against each blacklist, you simply enter either a server IP or domain name. MXToolBox then displays a table with each blacklist in its database. It also shows you why they blacklisted you. You may also instruct MXToolBox to monitor your mail address and notify you if it ever gets blacklisted. Other email blacklist checkers are DNSBL.info and Multirbl.valli.org.

Step 2: Send an inquiry to find out why you’re on a blacklist and what should be fixed

Having seen why you landed on a blacklist, the next thing is to send an email to the blacklist service. The email service provider may also contact the blacklist owner directly and let you know what you need to do to fix the problem in your email and lists. Once fixed, send an email back, explaining you’ve fixed all issues and ask to be removed from the blacklist. Finally, be sure to set your house in order. If necessary, establish an email sending policy for your company so as to forestall future blacklisting. 

Be Good — Don’t Get Blocked

The essence of maintaining a mailing list and sending out emails to your subscribers is to keep your prospective clients reminded of your offerings, generate new leads, and increase your conversion and click-through rates. And while at it, you have the opportunity to continue to build your brand’s credibility. However, if you practice unhealthy email policies such as buying a mailing list or sending out spam content, your email deliverability will suffer. Worse still, if your domain or IP address is flagged, it will be blacklisted. 

You want to avoid this because it affects your email campaigns and slows down business. So from time to time, you may use any free email blacklist checker to check if you are blacklisted or not. And if you are, simply get in touch with the owners of the email blacklist, and they’ll tell you what to do to fix the issue.

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FAQs about Email Blacklists

How do I check if my email is blacklisted?

You can know for sure by checking on any of the many free blacklist checkers out there. You may Google the websites and pick anyone. 

Alternatively, you can keep an out for bouncing emails. If your emails bounce back a lot, you should check to ascertain your status. You also use indicators like open rates, click rates, and email sending reputation to find out.

How do I stop my email from being blacklisted?

It’s easy to avoid getting on an email blacklist. Avoid buying mailing lists, send great content that’s optimized for both computer and mobile devices, monitor your email statistics closely, and be sure to segment your mailing list.

How many emails can I send without getting blacklisted?

This is the rule: starting with large lists will get you into trouble, especially if the bounce rate is high. 10% and above will typically get you blacklisted. Therefore, start small, warm up your IP address, and build your reputation. 150 – 400 emails a day is perfect. As your list grows, you’ll know when to gradually increase its size.


Anastasia Kryzhanovska

Anastasia Kryzhanovska
Senior Content Manager

Anastasia is a content marketer and manager with a strong IT background, passionate about storytelling and SEO. She likes creating high-quality content and helping others develop their skills. Besides work, she loves traveling, extreme sports, and reading fantasy books.

Published on December 4, 2020

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