Building an email list takes time and effort, but all of your efforts could be wasted if you get blacklisted. Email blacklists and other spam filters keep your emails from reaching their target audience, preventing you from receiving the best outcomes. Let’s understand how email blacklists function and how to avoid them.



What does "blacklisted" mean?

Email blacklists are real-time lists of domains or IP addresses that have been identified as spam senders. Blacklists are used by free mailbox providers, anti-spam vendors, internet service providers (ISPs), and email service providers (ESPs) to keep spam out of their systems.

If you are reported by blacklist operators, you will be added to the list and your content will be blocked, preventing your emails from reaching your recipients' inboxes. If your company gets banned, your email marketing ROI will suffer.


Why and how do domains get blacklisted?

There are some specific internet organizations that keep and maintain domain IP lists that are known as having spammer activity. An example of these organizations is MAPS: Mail Abuse Prevention System. Sources of spam can be many such as those that have open relays, spread spammy marketing software, and host certain types of websites. These can often be found in blocklists.
Mail servers, like the one you open your emails on (Outlook, Gmail..) are configured to consult these lists automatically when receiving an email. The mail server searches in the DNS for the  IP or domain address. This is the process that determines whether or not an email gets to the inbox or bounces.
If the mail server that is on the receiving end confirms that the email is in these blacklists, it signals an error back to the sent email client and doesn't accept the email. Otherwise, if the said mail server clears the domain, the receiving end assumes the email came from the safe source and delivers the email. So how do domains and emails end up in the blacklists? 

  • Spam complaints: ISPs may blacklist you as a result of complaints about your emails exceeding the permitted threshold.
  • Email content: Some Internet service providers (ISPs) filter emails based on keywords. You may be blacklisted if you use phrases like "money-back guarantee" and "free," as well as for using multiple exclamation marks and all caps.
  • Ineffective email list management: Unnoticed unsubscribe requests result from poorly managed email lists, which might get you being detected and blacklisted. If you don't verify your email list and continue to send subscribers emails even after they unsubscribe, users may mark you as spam.
  • Sending identical emails: When you send nearly similar emails to a large number of people, it triggers spam signals. Emails that are not personalized are considered spam since they include no useful information for the recipient.
  • Violation of daily sending limits: ISPs will be alerted if a company sends a large number of cold emails per day. It will also be regarded as spam if the interval between such emails is non-existent or identical.


How can you find out if your company domain is on a blacklist?

If you notice that your domain might be blacklisted, look at the statistics from your email campaign, such as clicks and domain opens. For example, sharp open drop-offs could signal that you've been blacklisted by an ISP. It happens when a recipient marks an email as spam or unsubscribes from your newsletter.

Delivery rates are deteriorating. This happens when your emails are deleted before the recipient opens them.

A high number of email bounce rates. It happens when your emails are unable to be delivered to the email addresses on your list and are returned to you.

To avoid being blacklisted, use appropriate email sourcing practices, manage and monitor your email campaigns, and follow email marketing tips.


7 best ways to avoid being blacklisted 

Being blacklisted is harmful to domains and their businesses as they deny the deliverability of business emails and therefore the loss of potential clients, business deals and new prospects. 

How can one avoid ending up in such lists?

  • Avoid spam email content

There are several keywords that are strongly linked to spam and should be avoided. Some examples are free, money, risk-free, apply now, etc. Furthermore, excessive use of exclamation marks and other punctuation, as well as capitalizing words, screams spam.

  • Don’t purchase lists

Buying email lists is a bad idea. They're generally riddled with spam baits from blacklists or old and useless emails. These lists will reduce your campaign's conversions and end up costing you more money in the long run. Rather, go with dependable on-demand quality data partners. They can supply GDPR-compliant data that has been checked and does not contain any invalid email addresses.

  • Personalize your message

Yes, this will take time, but that is just the goal. You don't want to send your users the identical templated message because that's what a spammer would do. You should personalize at least the first line of your message by stating something unique about them based on your research.

Not only will this demonstrate to the ISPs that each message is unique, but it will also enhance your email engagement because your prospects will notice that you took the time to research them first.

  • Adjust the volume and intervals of sending

You're more likely to end up on an email blacklist if you send too many emails every day at the same time. Keep the number of emails sent per day per mailbox below 100. Ensure that the time gap between emails is not a predetermined period of time, such as exactly 20 seconds.

In general, it's best to make your campaigns appear as human as possible. It should seem as if you are manually sending emails to friends.

  • Use double opt-in

This is a two-step verification process. The user will receive an email asking them to confirm their subscription after signing up for your mailing list. This method ensures that all of your subscribers are real individuals.

It also confirms that the user wants to receive your emails, such as new product announcements, promotional offers, or newsletters. You can lessen complaints about email spamming and lower unsubscription rates by using the double-opt-in method.

  • Make sure your SPF and DKIM are correctly set up

SPF (Sender Policy Framework) anti-spoofing mechanism evaluates whether an incoming email from a domain was sent by a host that is authorized to send mail for that domain. So, by implementing an SPF record, you prevent domain spoofing. 

DKIM (DomainKeys Identified Mail) is an authentication protocol that allows the sender of the email to have a "digital signature" on outgoing emails. This signature can be then verified by the email recipient's mail provider through DNS. DKIM protects emails from tampering and offers a guarantee of authenticity.

  • Avoid manually entering email addresses and include an unsubscribe link

Anti-spam legislation might result in your company's domain being blacklisted, so make sure your email messages include an unsubscribe link. This will keep you compliant with laws and regulations while also improving the customer experience of your subscribers. To ensure that your communications are only sent to people who want to receive them, provide an unsubscribe link in your emails.

To avoid mistakes in their email addresses, avoid manually entering your contacts into your database. This prevents you from sending messages to non-existent email addresses.

Also, don't add contacts to your email list who haven't agreed to receive your marketing emails. People who haven't granted you permission are likely to report your emails as spam, which will result in you being blacklisted.



Your chances of being blacklisted will considerably be decreased if you follow these tips. These procedures will help ensure that your emails are encrypted, users are authenticated, and spambots cannot send mails from your network. To avoid being blacklisted, practice good email hygiene, adhere to anti-spam regulations, and employ best email marketing practices.



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