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What are Email Blacklists and What can You do to Avoid Them

  • On 31/10/2019

Most email marketers have found themselves on at least one IP or domain blacklist at some point. If you find yourself on a blacklist, it’s a good idea to assess your address collection practices, evaluate your sunsetting policy, and then request a delisting at the relevant blacklist removal form (if they’re available).

The impact of having your IP or domain on a blacklist can range from being a small annoyance to a complete showstopper for your email deliverability. Because deliverability is the primary concern for most email marketers, it’s important to have an understanding of how blacklists function, and what you can do as a sender to reduce your risk of being blacklisted.

What is an email blacklist?

A blacklist is a real-time list that identifies IP addresses or domains that are known to send spam. They’re used by organizations like internet service providers (ISPs), free mailbox providers, and anti-spam vendors to prevent spam from coming into their systems. An individual or ESP can find their IP(s) or domain(s) on one or more blacklists depending on the amount and quality of the email and lists they’ve sent to.

While it may seem annoying to have the emails you’re carefully crafting rejected before they even reach your subscribers, blacklists are actually quite helpful. Nearly 85% of emails sent daily is considered spam, so blacklists exist to keep a huge amount of unwanted messages out of people’s inboxes. Very large ISPs have their own internal blacklists, but many use publicly available ones run by companies that specialize in this field and here’s how most of them work.

Spamhaus dnsbl diagram

In short, you send your email (Sender) and it’s received by an ISP (Receiver) who then decides if your email looks legitimate. If the ISP is using a blacklist, the email IP address is checked against the list. It then goes through the spam filters of the ISP to check for anything they don’t allow. If the email passes these tests, it’s sent to the inbox. The actual rejection of an email will come down to the policies of the ISP, as a blacklist is just one of the tools used to decide if an email is legitimate or not.

Which blacklists should you worry about?

The following blacklists are highly regarded and widely used by ISPs. They are reliable and professionally maintained, and being listed on one of them may have a significant impact on your email deliverability.

  • Spamhaus (SBL, XBL, DBL)
  • SpamCop (SCBL)
  • Composite Blocking List (CBL)
  • Passive Spam Block List (PSBL)
  • Invaluement
  • Spam URI Realtime Blocklists (SURBL)

Spamhaus is the gold standard of email blacklists, but all of the above are serious. If you’re on one, deal with it as fast as possible.

How to find out whether you are blacklisted or not?

Being confident is good but overconfidence can lead you to trainwrecks. Rather than wondering whether your email is blacklisted, you need to be sure that you are not on any email blacklist. To check whether you are blacklisted you need to follow the steps mentioned below:

Step 1: Run Test

To check if there is an issue with your email, you should always carry out a test using the following tools:

  • Mail-Tester
  • Glockapps
  • Isnotspam

When you open any of these sites, they will ask you to send an email to their email address. After receiving the email, they will analyze your email and let you know how spammy your email is. Make sure you also do the suggested changes.

Step 2: Check through Blacklists.

If you track the engagement and you find that they are dripping low, you can blame blacklists. You need to do a manual check on various blacklists to find out the reason for your reducing open rates. These blacklists are publically available. You can check directly through your domain name on some of the spam lists mentioned above. If you find out that you are listed on one of the blacklists, you need to make a removal request by confirming with them that you are not a spammer. You will be delisted once a confirmation message is received. This entire process takes around 24 hours.

Common reasons why IP/domains get blacklisted

ISPs (Internet Service Providers) like Yahoo, Gmail, and Outlook use spam filters to decide whether an email is delivered, flagged as suspicious, or rejected entirely.

Getting your emails past spam filters is crucial in email marketing to prevent your work ending up in the junk folder or worse – on an email blacklist!

If you wind up on an email blacklist, this means your IP or domain has shown characteristics of engaging in spam-related activity.

The definition of spam varies according to different ISPs and blacklist vendors. While each blacklist has its own set of rules and policies to determine spam, here are some of the typical reasons for getting blacklisted:

  • Recipient complaints
  • Emails or IPs being used for fraudulent activities (malware, phishing, hacking, ransomware, etc.)
  • IP supporting spam services like scrapers or bulletproof hosting
  • Buying email lists
  • Getting caught in spam traps
  • Using ISPs like Gmail or Outlook to send mass emails
  • Any other behavior considered suspicious (a high volume of hard bounces, too many emails sent within a certain period of time, technical standards not being met)

What to do if you get blacklisted

The first thing to do: Don’t panic. There are hundreds of blacklists in the world and the chances are good your IP address is on at least one of them. For the most part, this won’t impact your ability to reach your customers too much. Smaller blacklists are less likely to be used by big ISPs, and your address will probably drop off fairly quickly.

However, if you are on a blacklist, it could be an indicator that something is going wrong in your email marketing. The larger lists that are used by ISPs can have a bigger impact on your emails being delivered and your business in turn.

If your personal IP address is flagged and added to a blacklist you’ll need to contact the list about being removed. Each of the major blacklist companies have information on their sites on how to be removed from their lists. Usually, the process is fairly simple and straightforward, just be sure to do what they ask to clean up your emails and lists. For smaller lists, if you continue to mail and not run into a lot of spam complaints the IP address should drop off on its own. To check to see if an IP address is on a blacklist, go to MX Toolbox.

If you’re mailing through an email service provider, they’ll let you know what you need to do to fix the problem in your email and lists. They’ll contact the people who run the blacklists to get their IP address removed so they can continue sending. But you may find your account blocked until you can clean up your lists.

How to Avoid getting blacklisted in the first place?

Only email contacts who have subscribed to your email program — and never email contacts scraped from websites, third-party sources, or purchased contact lists. Clean your email lists on a regular basis. Never manually enter email addresses into your database or mass email these types of contacts. Validate your new subscribers’ email addresses. However, keep in mind that of all the things said, the best solution to reducing the chances of landing in any blacklists cannot be found in an exhaustive list.

Tips to avoid being blacklisted varies from industry to industry, and it is necessary that you update yourself with changing email deliverability laws. Blacklists do not exist to make your life harder but to ensure that there is no malpractice while you send emails to the mass. Hence, make sure you are providing good and valuable content to your recipients. That’s the best tip anyone will ever give you to avoid email blacklist. Comment down below if you have any doubts regarding the same.



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