What is the impact of the SORBS blacklist on B2C email deliverability?

Key findings

• Minimal impact: Most B2C senders experience little to no discernible impact from a SORBS listing on their deliverability to major mailbox providers. This is in contrast to other more influential blocklists.
• Historical relevance: While SORBS was once more widely used, its effectiveness and trustworthiness declined due to past management decisions, leading many larger ISPs and mailbox providers to reduce or cease their reliance on it.
• Niche use: Any current impact is typically limited to smaller, regional ISPs, homebrew filters, or specific markets (e.g., some in Russia, Greece, or Australia) that might still reference the list.
• Canary signal: A SORBS listing, while not directly impactful for most, could occasionally serve as an early warning or canary of underlying email program issues that might lead to listings on more impactful blocklists or poor reputation with major providers.
• Overlap with other systems: There can be some overlap between SORBS's spam traps and those used by larger security vendors, meaning a SORBS listing might indirectly indicate issues that could affect filtering by those vendors.

Key considerations

• Prioritize major blocklists: Focus your efforts on managing your reputation with the most influential blocklists and directly with major mailbox providers. Understanding how email blacklists actually work is essential for effective deliverability.
• Investigate root causes: If you find yourself listed on SORBS, it's wise to investigate the underlying reasons for the listing. This could point to issues in your sending practices that might eventually affect your overall domain reputation.
• Maintain list hygiene: Regularly clean your email lists to remove inactive or problematic addresses to prevent hitting spam traps, which are often the cause of blocklist listings, regardless of the list's overall impact.
• Understand blocklist dynamics: Recognize that the relevance of blocklists changes over time. Many older lists become less impactful as new filtering technologies emerge and take precedence.

Key opinions

• Low impact: Many marketers report seeing no real impact on their B2C sending, even when their IPs were listed on SORBS. This suggests that major B2C mailbox providers do not heavily rely on this specific blocklist.
• Shared IP challenges: For those using shared IP pools, getting listed on SORBS was once a common occurrence, particularly for senders with mixed B2B and B2C clients, yet B2C impact remained negligible.
• Minimal bounce data: Analysis of bounce data often shows an extremely low percentage of bounces attributed to SORBS, reinforcing its limited use by recipient servers.
• Industry perspective: The general sentiment among email marketers is that SORBS is not a significant factor in B2C email deliverability strategies, and there's often relief when this assessment is confirmed by others.
• Focus on reputation: Instead of chasing minor blocklist listings like SORBS, marketers are advised to focus on improving overall domain reputation and adhering to best sending practices.

Key considerations

• Don't overreact: If you receive a bounce report mentioning SORBS, it's generally not a cause for panic for B2C mail. Confirm its actual impact with your own delivery data before taking drastic action.
• Regional variations: While global impact is low, some specific geographical areas or smaller local ISPs might still rely on it. Keep an eye on your deliverability metrics for particular regions.
• Focus on core issues: Often, being listed on a minor blocklist is a symptom of broader issues, like poor list hygiene or sending unwanted mail. Addressing these fundamental problems will have a much larger positive effect on your email deliverability.
• Understand blocklist hierarchies: Not all blocklists carry the same weight. Familiarize yourself with the ones that truly influence major providers. As Klaviyo notes, SORBS typically has a much lower impact compared to other major blocklists.

Key opinions

• Marginal statistical impact: Historical data showed that SORBS accounted for a tiny fraction (as low as 0.005%) of all email bounces, indicating very limited usage by recipients.
• Trust degradation: The credibility of SORBS suffered significantly in the past due to controversial actions, such as listing entire ESPs, which led many large postmasters to abandon its use.
• Integrity of blocklists: The only thing blocklist operators have going for them is their integrity and trustworthiness. A breach of this trust, as seen with past SORBS actions, can severely undermine their effectiveness.
• Misinterpretation of listings: Experts warn against misinterpreting a listing on a less influential blacklist, like SORBS, as the primary reason for deliverability issues. Often, poor sending practices are the true cause, and the blacklist is merely a symptom.
• Proofpoint connection: While Proofpoint acquired SORBS, the lists are run independently. However, SORBS data is part of the broader data Proofpoint uses, meaning an overlap in spam traps could exist.

Key considerations

• Historical context matters: Understanding the history of a blocklist, including its past controversies, is crucial for assessing its current influence. As Word to the Wise highlighted, trust once broken is hard to regain.
• Focus on reputation fundamentals: Ensure your email program is adhering to best practices, regardless of specific blocklist listings. This includes maintaining strong email authentication and managing subscriber engagement.
• Don't attribute deliverability issues to minor lists: If emails are going to spam, look beyond minor blocklists. Major factors like poor sender reputation with Google or Yahoo, spam trap hits, or content issues are typically more impactful.
• Scrutinize claims: Be skeptical of claims that major ISPs heavily rely on certain blocklists, especially when based solely on DNS queries to those lists. Actual filtering decisions are often far more complex.

Key findings

• Reduced relevance: Many email service providers and deliverability guides now classify SORBS as a blocklist with much lower impact compared to other more influential lists like Spamhaus.
• Official closure: Recent reports confirm the closure of SORBS, rendering any past concerns about its impact largely irrelevant for ongoing email operations. This definitively signals its end as an active threat to deliverability.
• General blocklist principles: Documentation emphasizes that blacklists (or blocklists) are crucial for maintaining email territory order, but their individual impact on deliverability can vary greatly, with some having severe consequences and others having minimal.
• Severity of impact: When an IP or domain is listed on a blocklist, it directly affects delivery rates and can lead to emails being blocked or sent to spam folders. However, this impact is heavily dependent on which specific blacklist is involved.

Key considerations

• Stay informed: Regularly check official announcements and reputable deliverability resources for updates on blocklist relevance and operational status. Relying on outdated information can lead to misdirected efforts.
• Distinguish between lists: Always understand that not all blocklists are created equal. Focus your monitoring and remediation efforts on the lists that major ISPs and mailbox providers actively use.
• Prioritize best practices: Adherence to email deliverability best practices, such as maintaining healthy sending reputation and list hygiene, remains the most effective strategy to ensure inbox placement, regardless of the status of individual, less influential blocklists.
• Impact of closure: The closure of SORBS means that any previous reliance on it for spam filtering by some entities will now require exploring alternative solutions, but it generally will not negatively impact existing senders if it was not already a major factor.