How to get removed from the Spamhaus Hash Blocklist (HBL)?

Key findings

• Content-based listing: The HBL primarily targets the hash of email content, including subjects, bodies, and URLs, rather than sender IP or domain reputation.
• Underlying issues: HBL listings often indicate the presence of malicious content, compromised links, or issues with email list acquisition, such as 'lack of COI' (Confirmed Opt-In) which Spamhaus often references. These issues require investigation beyond just IP or domain reputation, as covered in our guide on what causes Spamhaus blocklisting.
• False positives: While less common, false positives can occur. Spamhaus encourages reaching out if you suspect a legitimate email hash has been listed. Checking the Spamhaus resource center can provide further context.
• Impact and resolution: The impact can vary, but generally, HBL listing prevents affected emails from reaching inboxes. Resolution involves identifying and removing the problematic content. Changing your sending address without addressing the root cause is not an effective long-term solution and may escalate to a DBL listing.

Key considerations

• Content review: Thoroughly review recent email content, including subjects, body text, and especially all linked URLs, for anything suspicious or unexpected. Look for signs of compromise on your website or sending platform if links are involved.
• Audience and opt-in: Evaluate your list collection practices to ensure strong Confirmed Opt-In (COI) processes are in place. Spamhaus often flags issues related to aggressive or sloppy list collection methods that lead to sending to unengaged or potentially problematic addresses (e.g., spam traps).
• Direct communication: Contact Spamhaus directly via their website (using the HBL FAQ) to seek more details about the listing and initiate a removal request if you believe it's a false positive or have resolved the issue. They will provide guidance on the specific hash and reason for listing.
• Monitoring: Implement continuous blocklist monitoring to quickly detect any future HBL listings or other blocklist issues, which is crucial for maintaining good deliverability.

Key opinions

• False positive concerns: Many marketers suspect false positives, especially when their email content seems innocuous and not explicitly malicious.
• Impact awareness: Some marketers are initially unsure about the precise impact of an HBL listing on their deliverability, with anecdotal evidence suggesting varied regional impacts (e.g., more noticeable in Europe than North America).
• List quality issues: There's a strong correlation observed between HBL listings and sloppy or aggressive list collection practices, even if outright purchasing lists isn't occurring.
• Limited visibility: Marketers frequently find it challenging to pinpoint the exact 'bad data' that led to the listing without more detailed information from Spamhaus.

Key considerations

• From address: Since HBL can target the 'From' address hash, some consider changing it, though this is only a temporary fix if the underlying content issue persists.
• Investigate linked content: Marketers must investigate if their website or any linked URLs are compromised, as HBL frequently catches malware or suspicious URLs.
• Geographical impact: Consider the geographical distribution of your audience, as HBL impacts might vary (e.g., more prevalent in Europe for some senders). This connects to the broader subject of email deliverability issues across different regions.
• Proactive prevention: Focus on robust opt-in processes and regular list cleaning to prevent issues that could lead to HBL listings. More details can be found in the Spamhaus HBL FAQs.

Key opinions

• Broad scope: HBL captures various threats, including content related to crypto wallets, malware, and compromised URLs, indicating a wide range of potential triggers.
• Root cause focus: Experts stress that listings are typically caused by underlying issues like hitting spam traps in large volumes, even if the sender believes their content is clean. This often points to issues with the email list itself.
• Beware of quick fixes: Changing a sending address without addressing the behavior that caused the listing is ineffective and can lead to more severe blocklistings, such as a DBL entry.
• Client-driven issues: For platforms handling multiple senders, a few problematic clients can cause HBL issues across the entire platform, requiring robust client vetting and monitoring.

Key considerations

• Verify website security: Prioritize checking if your website is compromised, especially if you're sending links, as this is a common source for HBL listings.
• List acquisition audit: Rigorously audit your email address acquisition processes to prevent 'lack of COI' issues or accidental collection of addresses that act as spam traps.
• Engage with Spamhaus: If you suspect a false positive, reaching out to Spamhaus directly is the most effective approach. They have processes in place to investigate such claims.
• Long-term behavior: Focus on correcting the underlying behavior that led to the listing. Only by fixing the source of the problem can you ensure a lasting resolution and prevent future blocklistings. This aligns with broader strategies for understanding email blocklists.

Key findings

• Content focus: HBL primarily focuses on email content, including subjects, body, and embedded URLs, making it different from IP or domain blocklists.
• Malicious content: It's designed to catch emails containing specific threats like malware, phishing, or other types of unsolicited bulk email, often identified by unique content hashes.
• Temporary listings: HBL listings are often dynamic and can expire automatically if the detected problematic content ceases to be sent, reflecting its role in real-time threat mitigation.
• False positive channels: Documentation usually provides clear channels for users to inquire about or request removal for potential false positives, indicating a willingness to review legitimate cases.

Key considerations

• Message structure: Minor changes to email content can alter the hash, but the underlying spamming behavior must be stopped to avoid new hashes getting listed.
• Reputation implications: While HBL targets content, repeated listings can indirectly harm overall sender reputation, potentially leading to listings on other blocklists.
• Collaboration: If you are an ISP or Email Service Provider, Spamhaus documentation often advises collaboration to resolve underlying issues that lead to HBL listings originating from your networks, as highlighted in Spamhaus's documentation.
• Proactive measures: Best practices for email marketing, like robust opt-in and regular list hygiene, are crucial to avoid HBL listings, even if the content seems benign.