Summary
The consensus from marketers, experts, and documentation is that the significance of a blocklist depends on its adoption rate by major ISPs and corporations, its relevance to the recipient's mail server, and the rigor of its listing/delisting process. Lists with low usage, pay-to-delist options, or those focusing on dynamic IPs without concrete spam evidence are often deemed insignificant. Some humorous examples highlight the range of blocklist quality. Prioritizing widely-used lists (like Spamhaus and Proofpoint) and considering audience-specific usage patterns is crucial.
Key findings
- Adoption Determines Impact: A blocklist's significance largely depends on its adoption by major ISPs, email providers, and reputation systems.
- Pay-to-Delist = Red Flag: Blocklists offering immediate delisting for a fee are often viewed skeptically and may not be effective.
- Relevance by Recipient: The impact of a blocklist is directly related to whether it's used by the recipient's email provider.
- Focus on Major Lists: Focus on major, widely-used blocklists like Spamhaus and Proofpoint is more critical than monitoring smaller, less utilized lists.
- RFC Ignorant and Google: Being on RFC Ignorant may be a problem if you use Google Workspaces.
Key considerations
- Evaluate Audience: Understand the email providers used by your target audience and prioritize monitoring blocklists relevant to them.
- Delisting Processes: Assess the listing and delisting processes of a blocklist. A rigorous process indicates higher credibility.
- Reputation Systems: Recognize that reputation systems like Cisco Talos, BarracudaCentral, and Proofpoint influence deliverability.
- Beware Retaliation: Be cautious when publicly criticizing blocklists, as there is a risk of retaliatory blacklisting.
- Dynamic IP Lists: Be aware blocklists focusing purely on dynamic IP addresses, without confirming spam activity, may not be useful.
What email marketers say
12 marketer opinions
The provided answers converge on the idea that not all email blocklists are created equal, and many are insignificant or ineffective. Factors determining insignificance include low usage by major ISPs and corporations, pay-to-delist options, improper validation processes, limited reach, and focusing on dynamic IPs without specific spam evidence. The general consensus is that marketers should focus on the widely-used and reputable blocklists monitored by significant mailbox providers rather than getting caught up in less relevant or smaller lists.
Key opinions
- Limited Impact of Small Lists: Smaller, less reputable blocklists often have a limited impact on overall email deliverability. Listings on these lists should not be a major concern.
- Pay-to-Delist is a Red Flag: Blocklists offering immediate delisting for a fee are generally viewed with skepticism, as their effectiveness is questionable.
- Relevance Varies by Recipient: The relevance of a blocklist is directly proportional to its usage by the intended recipient. If the recipient's mail server uses a particular blocklist, it becomes relevant, regardless of overall size.
- Focus on Major Lists: Focusing on widely-used blocklists monitored by significant mailbox providers is more critical for email deliverability. Examples include Spamhaus and Proofpoint.
Key considerations
- Recipient Usage: Assess which blocklists are used by your target audience's email providers to determine relevance.
- Reputation & Validation: Prioritize monitoring blocklists with rigorous validation processes and a strong reputation within the industry.
- Delisting Process: Be wary of blocklists offering easy, paid delisting, as this undermines their credibility.
- Context Matters: Consider the context of the listing and whether it is impacting actual delivery rates before taking action.
Marketer view
Marketer from Email Geeks shares an opinion that all blocklists are insignificant until one lists you that is used by someone you are trying to mail.
17 Feb 2023 - Email Geeks
Marketer view
Email marketer from MailerMailer responds that some RBLs may be considered insignificant based on their limited reach and impact on overall email delivery rates. It's essential to focus on widely-used blocklists.
28 Dec 2022 - MailerMailer
What the experts say
5 expert opinions
Experts emphasize focusing on actively used blocklists by major ISPs and corporations, as these are most relevant. Smaller, less maintained lists may be ignored, but relevance depends on the recipient's usage. One expert recounts being blocklisted in retaliation for criticizing a blocklist. RFC Ignorant impacts Google Workspace users. Humorous examples include lists promising no false negatives or blocking IPs with the number 7.
Key opinions
- Focus on Active Blocklists: It's often safe to ignore listings on blocklists not actively used by major ISPs and corporations.
- Recipient Usage Matters: The relevance of a blocklist depends on its usage by recipients' email providers.
- RFC Ignorant and Google: Being on RFC Ignorant may be a problem if you use Google Workspaces.
- Blocklists Aren't Always Serious: Some blocklists have been created with humorous or ineffective criteria.
Key considerations
- Potential Retaliation: Be cautious when publicly criticizing blocklists, as it could lead to retaliatory blocklisting.
- Audience-Specific Relevance: Determine if the blocklist is used by the email providers of your target audience.
- Evaluate Blocklist Criteria: Consider the criteria used by a blocklist before taking action; some may be arbitrary or ineffective.
- Monitor Google Workspace: Be aware that RFC Ignorant may impact deliverability for Google Workspace users.
Expert view
Expert from Email Geeks recalls examples of humorous or ineffective blocklists, including nofalsenagatives.samspade.org and a list that blocked every IP with a 7.
26 Feb 2023 - Email Geeks
Expert view
Expert from Email Geeks advises caution when criticizing blocklists, recounting an experience where criticizing a blocklist resulted in their employer's IPs being blocklisted.
6 May 2025 - Email Geeks
What the documentation says
6 technical articles
Documentation from various sources highlights that the effectiveness of a blocklist is largely determined by its adoption rate and scope. Smaller, less maintained RBLs, private blocklists, and those with narrow focus areas (e.g., dynamic IP ranges without spam evidence) are unlikely to have a widespread impact on deliverability. Blocklists that don't influence major ISPs, email providers, or reputation systems (like BarracudaCentral, Proofpoint, and Cisco Talos) have limited reach.
Key findings
- Low Adoption = Low Impact: Less maintained or smaller RBLs have limited impact due to low adoption rates among major ISPs and email providers.
- Scope Matters: Blocklists with a narrow focus, such as dynamic IP ranges without specific spam evidence, may be less effective.
- Private Lists Have Limited Reach: Smaller, private blocklists used by only a few organizations have a limited impact compared to widely adopted lists.
- Influence on Major Providers: Blocklists not influencing major providers or reputation systems have limited reach.
Key considerations
- Adoption Rate: Consider the adoption rate of a blocklist by major ISPs and email providers when evaluating its relevance.
- Scope of Blacklisting: Assess whether the blocklist focuses on specific spam evidence or broader, less reliable criteria.
- Targeted Networks: Understand which networks or systems a blocklist influences (e.g., Barracuda-protected networks).
- Reputation Systems: Recognize that reputation systems like Cisco Talos, BarracudaCentral, and Proofpoint have a significant impact on deliverability.
Technical article
Documentation from BarracudaCentral explains that its reputation system impacts delivery to Barracuda-protected networks. Blocklists not influencing major providers may have limited reach.
29 Jul 2021 - BarracudaCentral
Technical article
Documentation from URIBL.com answers that URIBL focuses on URI-based blacklisting. Lists focusing on dynamic IP ranges or IPs with poor reputation, but lacking specific spam evidence, may be less effective.
13 Jul 2024 - URIBL.com
Besides Spamhaus, what blocklists are important for email marketers to monitor?
How can I get delisted from Spamhaus?
How can I get help with a Spamhaus listing delisting?
How do I determine the severity and mitigate different email blocklists?
How effective are RBLs and blocklists for preventing spam in 2022?
What are the most important email blacklists to monitor and how do you check them?
