Summary
A comprehensive approach to email deliverability necessitates understanding and strategically prioritizing blocklists. The importance of any particular blocklist depends significantly on the recipient's email provider and geographical location. Proactive monitoring of major blocklists like Spamhaus, Barracuda, and Proofpoint is crucial, but niche or regional lists should also be considered based on the target audience. Experts emphasize that domain-based lists are useful for identifying problematic customer content, while IP-based lists often signal severe issues. Some blocklists are not publicly available, requiring direct observation of blocked mail. Documentation from various sources highlights the specific purposes and functions of different blocklists, such as the Spamhaus SBL/DBL, Barracuda BRBL, Proofpoint DRF, and URIBL. Furthermore, it's crucial to view blocklists as diagnostic tools rather than definitive judgments, prompting investigations into underlying issues like list hygiene and account security. Relying solely on blocklists is insufficient; a holistic approach that includes sender reputation, engagement metrics, and email authentication methods (SPF, DKIM, DMARC) is essential for sustained deliverability.
Key findings
- Recipient Relevance: The importance of blocklists is highly dependent on which email providers your recipients use and their geographic location.
- Proactive Monitoring of Major Lists: Proactive monitoring of Spamhaus, Barracuda, and Proofpoint is crucial due to their widespread impact.
- Domain vs. IP Importance: Domain-based lists identify problematic customer content, while IP-based lists signal severe issues.
- Diagnostic Use of Lists: Blocklists should be used as diagnostic tools to uncover underlying problems like list hygiene and security issues.
- Comprehensive Deliverability Strategy: A comprehensive deliverability strategy requires more than just blocklist monitoring. Sender reputation, authentication, and engagement metrics are all vital.
- Impact of Specific Lists: Spamhaus listings directly damage delivery. SURBL listings correlate with poor email practices.
- Non-Public Lists: Some blocklists are not publicly available and require observation of mail being blocked.
Key considerations
- Tailor Monitoring to Audience: Tailor your blocklist monitoring efforts to the specific demographics and email providers used by your target audience.
- Investigate Underlying Issues: A blocklist listing should trigger an immediate investigation into potential list hygiene problems, compromised accounts, or other problematic sending practices.
- Prioritize Sender Reputation: Focus on improving and maintaining a positive sender reputation by following best practices for list management, engagement, and content creation.
- Implement Authentication: Ensure proper implementation of SPF, DKIM, and DMARC to improve email authentication and demonstrate legitimacy to mailbox providers.
- Monitor Domain and IP Reputation: Actively monitor both your domain and IP reputation to identify and address any potential issues that could lead to blocklisting.
- Use Multiple Monitoring Tools: Combine various tools and services to get a more comprehensive view of blocklisting status.
What email marketers say
11 marketer opinions
The importance and prioritization of email blocklists for deliverability depend on several factors, including the recipient's email provider, target audience, and the specific goals of the sender. Major blocklists like Spamhaus, Barracuda, and Proofpoint have a broad impact and should be proactively monitored. However, smaller or regional blocklists can be crucial for specific audiences. A comprehensive deliverability strategy involves monitoring blocklists, maintaining a good sender reputation, and employing email authentication methods.
Key opinions
- Blocklist Impact: The impact of a blocklist varies depending on the recipient's email provider. Major blocklists have a wider reach, while niche lists affect specific regions or industries.
- Monitoring Priority: Prioritize monitoring blocklists relevant to your target audience and those widely used by major mailbox providers.
- Proactive Monitoring: Proactively monitor key blocklists such as Spamhaus, Barracuda, and Proofpoint to identify and address deliverability issues early.
- Comprehensive Approach: Blocklist checks are part of a broader deliverability strategy that includes sender reputation, authentication, and engagement metrics.
- Multiple Tools: Using multiple tools and services for monitoring provides a more comprehensive view of your blocklist status.
Key considerations
- Regional Relevance: Consider the geographical location of your target audience when prioritizing blocklist monitoring.
- List Hygiene: Maintain clean email lists and sender reputation to avoid being listed on blocklists.
- Authentication: Implement email authentication methods (SPF, DKIM, DMARC) to demonstrate legitimacy and improve deliverability.
- Sender Reputation: Actively work to improve sender reputation and engagement metrics as these are critical to avoid blocklisting.
- Diagnostic Tool: Use blocklists as a diagnostic tool to identify underlying issues such as list hygiene problems or compromised accounts.
Marketer view
Email marketer from Email Marketing Forum shares to prioritize blocklist monitoring based on your target audience. If you primarily send emails to users in Europe, focus on lists that are commonly used by European ISPs and mailbox providers. Tailor your monitoring efforts to the regions and industries you serve.
20 Jun 2023 - Email Marketing Forum
Marketer view
Email marketer from Litmus says blocklists are like a giant blacklist for IP addresses and domains that have been associated with spam. If you land on one, your emails might not make it to the inbox.
1 Oct 2021 - Litmus
What the experts say
7 expert opinions
Experts emphasize that blocklists impact email deliverability differently and should be approached strategically. Spamhaus listings directly damage delivery, while SURBL listings correlate with poor practices. Domain-based lists are crucial for identifying problematic customer content, whereas IP-based listings indicate severe issues. Some blocklists are not public and require direct observation of blocked mail. Meaningful querying of DBL/URIBL requires access to email content, making it more relevant for ESPs. Blocklists are diagnostic tools, not definitive judgments, highlighting underlying problems. Relying solely on blocklists is insufficient; a comprehensive view including engagement and sender reputation is necessary.
Key opinions
- Spamhaus Impact: Being listed on Spamhaus directly damages email delivery.
- SURBL Correlation: SURBL listings correlate with poor email practices.
- Domain vs. IP Lists: Domain-based lists help identify bad customer content, while IP-based lists signal severe issues.
- Non-Public Lists: Some blocklists are private, requiring observation of blocked mail for detection.
- DBL/URIBL Querying: Meaningful querying of DBL/URIBL requires email content access, more useful for ESPs.
- Diagnostic Use: Blocklists are diagnostic tools, revealing underlying issues, not definitive judgments.
- Comprehensive View: Deliverability needs a comprehensive approach beyond blocklists, including engagement and sender reputation.
Key considerations
- Customer Investigation: Domain-based hits necessitate investigating customer content.
- Behavioral Monitoring: Dedicated IP listings indicate a need for improved behavioral monitoring.
- Underlying Issues: Blocklist listings should prompt investigation into list hygiene and account security.
- Engagement & Reputation: Prioritize building strong sender reputation and positive engagement metrics.
- Strategic Use: Use blocklists as part of a wider strategic view for deliverability not as the only element.
Expert view
Expert from Email Geeks shares to meaningfully query the DBL (or URIBL), you need access to the content of mail being sent, which is more useful for ESPs.
7 Jan 2022 - Email Geeks
Expert view
Expert from Word to the Wise shares solely focusing on blocklists is not enough for deliverability. A broader perspective, including engagement and sender reputation, is necessary to achieve consistent inbox placement, as some lists are poorly managed.
14 Jan 2025 - Word to the Wise
What the documentation says
5 technical articles
The documentation highlights several important blocklists and sender support resources that impact email deliverability. Spamhaus maintains lists like SBL (IP addresses of spam sources) and DBL (domains found in spam), each serving a distinct purpose. Barracuda Central's BRBL is a real-time database of IPs with poor reputations, used by Barracuda Networks for spam filtering. Proofpoint's DRF analyzes email traffic to identify and block spam based on sender reputation, while Microsoft provides sender support resources for deliverability to Outlook.com and Hotmail users. URIBL categorizes URLs found in spam, flagging malicious domains and phishing attempts. Understanding these lists and resources is essential for troubleshooting and improving email sending practices.
Key findings
- Spamhaus Lists: Spamhaus maintains distinct blocklists like SBL (IPs) and DBL (domains) for identifying spam sources.
- Barracuda BRBL: Barracuda's BRBL identifies IPs with poor reputations used for spam filtering.
- Proofpoint DRF: Proofpoint's DRF analyzes email traffic and sender reputation to block spam.
- Microsoft Sender Support: Microsoft provides resources for senders to ensure deliverability to Outlook.com and Hotmail users.
- URIBL Categories: URIBL categorizes URLs found in spam, flagging malicious domains and phishing attempts.
Key considerations
- List Differentiation: Understand the specific purpose of each blocklist for effective troubleshooting.
- Reputation Improvement: Listing on BRBL indicates the need for improved sending practices.
- Traffic Analysis: Recognize that Proofpoint analyzes traffic and sender reputation to identify spam.
- Microsoft Policies: Adhere to Microsoft's policies and best practices for optimal delivery to their users.
- Content Scrutiny: Be aware that URIBL flags URLs in spam for malicious content and phishing attempts.
Technical article
Documentation from URIBL explains their lists categorize URLs found in spam. Some lists focus on new or potentially malicious domains, while others flag URLs associated with phishing or malware. Understanding these categories is useful for identifying compromised content.
12 Jan 2023 - URIBL
Technical article
Documentation from Barracuda Central details the Barracuda Reputation Block List (BRBL) is a real-time database of IP addresses with poor reputations. It is used by Barracuda Networks' email security products to identify and block spam. If you find your IP address on the BRBL, it indicates that your sending practices need improvement.
26 Jul 2022 - Barracuda Central
Besides Spamhaus, what blocklists are important for email marketers to monitor?
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