Should I use blacklist or blocklist in email marketing?
Matthew Whittaker
Co-founder & CTO, Suped
Published 9 Aug 2025
Updated 15 Aug 2025
6 min read
The terms "blacklist" and "blocklist" are often used interchangeably in email marketing, but there is a growing conversation about which term is more appropriate. While "blacklist" has been the traditional term for lists of email senders or IPs identified as sources of spam, "blocklist" is gaining traction due to a push for more inclusive language and its clearer, more direct meaning in the context of email filtering. For email marketers, understanding both terms and their implications is vital for maintaining good deliverability.
My focus is always on helping businesses achieve peak email performance, and that includes staying current with industry terminology. The debate over "blacklist" versus "blocklist" reflects a broader trend toward precision and inclusivity in technical language.
Regardless of the terminology, the underlying goal remains the same: to prevent unwanted email from reaching inboxes. This article will explore the nuances of these terms, their impact on your email campaigns, and practical steps you can take to ensure your messages land where they belong.
Historically, "blacklist" was the standard term used to describe a list of entities (IP addresses, domains) that are denied access or blocked. This term has been deeply embedded in the lexicon of email deliverability for decades. However, with a broader societal shift towards inclusive language, many in the tech and marketing communities have begun advocating for "blocklist" as a replacement.
The preference for "blocklist" often stems from the idea that "black" in "blacklist" might carry negative connotations, similar to other terms that have been reconsidered. Beyond the social aspect, "blocklist" is also considered more descriptive of the actual function: it is a list that blocks. Many organizations are actively adopting more inclusive terminology, as evidenced by efforts like the Inclusive Naming Initiative.
It is not uncommon to also hear the term "denylist," particularly within security or enterprise IT circles, as an alternative to "blocklist." Regardless of the specific terminology, the core concept remains the same, these are lists designed to stop unwanted email.
Blacklist
This is the widely recognized and traditional term. While some view it as outdated or problematic due to its origins, it remains prevalent in much of the email industry's infrastructure and older documentation. It is generally understood to refer to a list of senders or IPs that are blocked.
Historically, this term was easy to grasp for many, signifying that something or someone was 'out' or 'forbidden.' However, it sometimes caused confusion with other types of lists, such as suppression lists, which serve a different purpose.
Blocklist
This term is gaining significant traction and is preferred by many for its clarity and inclusivity. It directly describes the function of the list, which is to block messages from specific sources. Major tech companies and industry organizations are increasingly adopting "blocklist" in their guidelines and documentation.
The adoption of "blocklist" reflects a move towards more precise and neutral language. It avoids potential negative connotations and accurately represents the action being performed (blocking), making it less ambiguous for new professionals entering the email space.
How blacklists and blocklists operate
An email blacklist (or blocklist) is essentially a database of IP addresses or domains that have been flagged as sources of spam or malicious content. These lists are used by internet service providers (ISPs) and email service providers (ESPs) to identify and reject incoming emails from suspicious sources, protecting their users from unwanted messages. You can learn more about how these lists function in our guide on how email blacklists actually work.
Being listed on a blocklist can severely impact your email deliverability. When your IP or domain is listed, your emails are likely to be blocked entirely or routed directly to recipients' spam folders, significantly reducing your reach and campaign effectiveness. This directly harms your sender reputation, which is built on consistent positive sending behavior. Understanding what an email blacklist is can help you avoid common pitfalls.
There are various types of blacklists (or blocklists), including public ones like those maintained by Spamcop or Spamhaus, and private ones used internally by individual ISPs like Gmail or Outlook. The impact and severity of being listed can vary greatly depending on the specific list. This highlights the importance of understanding which email blocklists are most important.
Key function of blacklists (blocklists)
These lists are integral to spam prevention, protecting inboxes from malicious or unwanted emails. Even legitimate senders can accidentally trigger a listing if their practices fall short of established guidelines.
Purpose: Identifies and filters out known sources of spam.
Mechanism: Blocks emails from listed IP addresses or domains.
Impact: Reduces inbox placement and affects sender reputation.
Navigating deliverability with precise language
For email marketers, the focus should always be on maintaining a clean sending reputation and ensuring high inbox placement, regardless of the terminology used. While "blocklist" is gaining favor, many email systems and older documentation still use "blacklist." It is wise to be familiar with both terms to effectively communicate and troubleshoot deliverability issues.
To avoid getting on a blacklist (or blocklist), it is critical to adhere to email marketing best practices. This includes sending only to engaged, opted-in subscribers, maintaining a healthy list by regularly removing inactive addresses, and monitoring your sender reputation. A high bounce rate, frequent spam complaints, or sending to spam traps are common triggers for being listed.
Regularly checking your domain and IP for blocklist presence is a proactive step. You can use our blocklist checker to see if your sending infrastructure is currently listed. If you find your domain or IP on a blacklist, understanding what happens when your domain is on an email blacklist and how to mitigate it is crucial for swift recovery.
Example DNSBL query for SpamhausBASH
dig +short 2.0.0.127.zen.spamhaus.org
Proactive monitoring and swift action are essential to mitigate the impact of any blocklist listing. Your sender reputation is a fragile asset, and consistent vigilance is key to protecting it.
Trigger
Description
Impact on deliverability
Spam complaints
Recipients marking your emails as spam.
Immediate negative impact, higher likelihood of being listed on private and public blocklists.
High bounce rates
Sending to invalid or non-existent email addresses.
Signals poor list hygiene, can lead to ISP throttling or listing.
Spam traps
Emails designed to catch spammers, often from old or harvested lists.
Strong indicator of questionable sending practices, often leads to severe blacklisting.
Poor content quality
Emails with spammy keywords, suspicious links, or deceptive practices.
Increases spam filter scores, resulting in emails landing in spam folders or being blocked.
Views from the trenches
Best practices
Always obtain explicit consent from recipients before sending any marketing emails to them.
Regularly clean your email lists to remove inactive or invalid addresses, reducing bounces.
Implement robust email authentication protocols such as SPF, DKIM, and DMARC.
Monitor your sender reputation closely using tools that provide insights into ISP feedback loops.
Craft engaging and relevant content that encourages positive recipient interaction.
Common pitfalls
Purchasing or renting email lists, which often contain spam traps and unengaged contacts.
Sending emails infrequently or in large, sudden bursts without proper IP warm-up.
Ignoring unsubscribe requests or making the unsubscribe process difficult for recipients.
Failing to address high bounce rates or spam complaint rates promptly.
Not setting up proper email authentication, leaving your domain vulnerable to spoofing.
Expert tips
Consider adopting "blocklist" and "allowlist" in your internal documentation for clarity.
Actively engage with email deliverability communities to stay informed about changes.
Understand that even legitimate senders can temporarily land on blocklists, making monitoring essential.
Prioritize building strong relationships with ISPs through good sending practices.
Leverage DMARC reporting to gain visibility into email authentication failures.
Marketer view
Marketer from Email Geeks says: We have started using the terms block/deny list and allow/safe list, which feels more precise and inclusive.
2020-12-02 - Email Geeks
Marketer view
Marketer from Email Geeks says: I have been consistently using the term blocklist, as it accurately describes the function of these lists.
2020-12-02 - Email Geeks
Clarity and impact in email marketing
In summary, while "blacklist" remains widely understood, "blocklist" is the preferred term in modern email marketing and deliverability circles. It is more precise, less problematic culturally, and aligns with the actual function of these systems. As an email marketer, embracing "blocklist" can demonstrate a commitment to contemporary and inclusive language.
More importantly than the specific term you choose is your unwavering commitment to email deliverability best practices. Consistently sending relevant, permission-based emails, maintaining a clean list, and promptly addressing any issues will safeguard your sender reputation. Whether you refer to it as a blacklist or a blocklist, staying off these lists is paramount for the success of your email campaigns.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
