Mailgenius guides

Why Is My Email Blacklisted? Pitfalls to Avoid

An email blacklist is capable of derailing your email marketing efforts and severing the communication lifeline between you and your audience. The term ‘blacklist’ might evoke a sense of foreboding, and rightly so. One misstep could lead to a cascade of undelivered emails, tarnished sender reputation, and lost opportunities.

If you are wondering why your email is blacklisted, then pay close attention.

In this comprehensive guide, we delve into the heart of email blacklisting, unraveling its definition, the different types of blacklists, and the common triggers that could land you on one.

Note: Ensure the deliverability of your emails by utilizing MailGenius’s blacklist checker to ascertain whether your IP is on any email blacklist. A blacklisted IP can significantly hinder your email campaigns by directing your emails to spam folders, thus preventing them from reaching your intended recipients. MailGenius’s email blacklist tester provides a straightforward and immediate solution to this issue by offering instant insights into your IP’s status. With its user-friendly interface, obtaining these crucial insights requires no technical expertise and is entirely free of charge for the first 3 tests.

The Definition Of An Email Blacklist

An email blacklist is a real-time database that identifies IP addresses or domains known for sending spam or malicious content. Once a mail server IP address or domain is listed on a blacklist, emails sent from that source are likely to be blocked or filtered into the spam folder, significantly impacting email deliverability.

There are various types of email blacklists, each maintained by different entities ranging from public organizations to private corporations and even independent security firms. Public blacklists are accessible to anyone and can be checked through various tools. On the other hand, private blacklists are maintained by mailbox providers like Gmail and Yahoo, which use these lists to filter spam internally. Besides, there are enterprise spam firewalls maintained by independent organizations like Barracuda and McAfee, which keep records of spam domains and addresses for corporate IT departments to ensure security against malicious email content.

In essence, an email blacklist serves as a protective shield for email recipients against potential spam and malicious content, while posing a significant challenge for marketers to ensure their email campaigns remain compliant with best practices to avoid being blacklisted.

Public blacklists

Public blacklists are databases accessible to anyone, containing IP addresses or domains known for disseminating spam or malicious content. They serve as a resource for individuals and organizations to check whether a particular IP or domain is flagged for undesirable email practices.


Private blacklists

Private blacklists are maintained by individual mailbox providers like Gmail and Yahoo. These lists are used internally to filter and block spam, ensuring a cleaner inbox for their users. Access to these blacklists is restricted, and email senders may require a license or special permission to view or interact with these lists.


How Do Businesses Get Blacklisted?

The criteria for landing on a blacklist can vary, but common triggers include a high number of spam complaints, poor email list hygiene, hitting spam traps, sudden spikes in email volume, or being identified as a source of malware or phishing scams.

A Huge Number Of Spam Complaints

One of the primary triggers for landing on an email blacklist is the accumulation of a significant number of spam complaints against your emails. When recipients mark your emails as spam, it sends a strong signal to Internet Service Providers (ISPs) and email service providers about the undesired nature of your content. This behavior, when noted in large volumes, can lead to your IP address or domain being blacklisted. It’s a protective measure taken by an email service provider to shield their users from potential spam or malicious content.

Bad Email Lists

A poorly managed email list is a direct ticket to being blacklisted. Bad email lists often contain old, stale, or illegitimate email addresses that can lead to a high bounce rate, indicating to ISPs that the emails being sent are not solicited or desired by the recipients. It’s imperative to exercise diligence while preparing and maintaining your email list. A poorly curated list may contain high bounced email addresses and spam traps set up by ISPs to catch spammers, further exacerbating the blacklisting issue.

Spam Traps

Spam trap are specialized email addresses or domains used by ISPs and email service providers to identify and monitor spam activities. They act as bait to catch spammers red-handed. There are three primary types of spam traps: recycled spam traps, new spam traps, and typo spam traps. Recycled spam traps are old email addresses that have been repurposed to catch spammers, while new spam trap addresses are created specifically for the purpose of trapping spam. 

Typo spam traps, on the other hand, are commonly misspelled domain names or email addresses. Landing in one of these traps can lead to immediate blacklisting, as it’s a clear indication of either poor list hygiene or malicious intent.

It’s crucial for email marketers to find and avoid spam trap email addresses by maintaining a clean and updated list.

An Unexpected Increase In Volume/List Size

A sudden surge in email volume or a drastic increase in list size can raise red flags with Internet Service Providers (ISPs). Such anomalies may suggest to ISPs that a business has either purchased an email list or engaged in other non-compliant email acquisition practices.

This unexpected hike can trigger spam filters, leading to a higher probability of your IP address or domain being blacklisted. It’s essential to grow your email list organically and maintain a consistent email sending volume to avoid arousing suspicion. Gradually increasing your email volume over time are prudent practices that can help maintain a healthy sender reputation. By adhering to industry best practices and avoiding abrupt changes in your email sending behavior, you can significantly reduce the risk of landing on a blacklist and ensure that your email marketing campaigns continue to reach the inboxes of your intended recipients.


The nefarious activities of hackers pose a significant threat to email deliverability. If hackers gain access to your email server, they can exploit it to send out a barrage of spam emails, tarnishing your sender reputation and leading to blacklisting. The malicious emails sent from your server can trigger spam filters and result in your IP address or domain being flagged and subsequently blacklisted.

Malware Infection

A malware infection in your system can have detrimental effects on your email deliverability. Malware such as viruses, spambots, and trojans can hijack your email server and use it to disseminate spam or malicious content. When emails sent from your system trigger spam filters due to malware activities, your IP address or domain stands a high chance of being blacklisted. This not only disrupts your email marketing efforts but also poses a severe threat to your system’s security and data integrity. Running regular anti-malware checks and ensuring your system’s security software is up-to-date are critical steps in preventing malware infections.

How To Avoid Blacklists

The repercussions of being blacklisted are severe as it hampers your email marketing efforts by reducing the chances of your emails reaching the intended recipients. Although there are ways to remove yourself from an email blacklist, it can still be a hassle to deal with. Therefore, understanding the mechanics of email blacklisting, and adopting strategies to avoid it, is crucial for maintaining a healthy email marketing ecosystem.

Spam Tests

Utilizing spam tests is a proactive measure to evade the dreaded email blacklist. Spam tests evaluate your email content, sender reputation, and other crucial factors against known spam filters and blacklisting criteria. By running your email campaigns through spam tests before hitting the send button, you can identify potential red flags that might lead to blacklisting. These tests check your domain name across various blacklists and provide insights into how your emails might be perceived by different email providers and spam filters.

MailGenius offers a spam email testing tool to help you to take remedial action in time if any issues are detected. By incorporating spam tests into your email marketing routine, you not only reduce the risk of blacklisting but also improve the overall deliverability and effectiveness of your campaigns. It’s an indispensable step towards ensuring that your emails reach the inbox of your recipients and your marketing messages are conveyed as intended.

Never Purchase Lists

Purchasing email lists is a perilous shortcut that often leads to the dreaded blacklisting. These lists are typically filled with outdated, incorrect, or unverified email addresses, and may also contain spam traps set up by ISPs to catch spammers. When you send emails to these addresses, the high bounce rate and interaction with spam traps send a clear signal to ISPs that your email practices are not compliant with industry standards.

Recipients who haven’t opted-in to receive emails from you are more likely to mark your emails as spam, further tarnishing your sender reputation. The repercussions are severe; your IP address or domain can be blacklisted, drastically hindering your email deliverability. It’s crucial to build your email list organically through legitimate opt-in methods. This way, you ensure that your recipients are interested in your content, significantly reducing the likelihood of spam complaints and blacklisting, and fostering a healthy, engaged audience for your email marketing campaigns.

Double Opt-ins

Employing a double opt-in process is a sterling practice to enhance the quality of your email list and significantly reduce the risk of landing on a blacklist. Unlike a single opt-in where users are added to your email list as soon as they provide their email address, a double opt-in requires a second step where the user must confirm their subscription, usually by clicking a link in a confirmation email. This two-step verification process ensures that the email address provided is valid and that the user is genuinely interested in receiving your emails. 

By filtering out uninterested recipients and eliminating invalid email addresses, the double opt-in process drastically reduces the likelihood of spam complaints and bounces, both of which are common triggers for blacklisting.

How To Find Out If You Are On A Blacklist?

Discovering whether your IP address or domain is on a blacklist is a crucial step towards maintaining optimal email deliverability. Various online tools and databases are available that can help you check your status across multiple blacklists. These tools provide a platform where you can enter your IP address or domain name and scan across a multitude of blacklists to see if you are listed. If a listing is found, these tools often provide additional information about the reason for the blacklisting and the steps you can take to get delisted.