Which major Mailbox Providers (MBPs) use Cloudmark for spam filtering?

Key findings

• Confirmed Users: Several major US-based ISPs, including Comcast, Cox, and Roadrunner, have historically used or currently use Cloudmark for spam and blocklist filtering.
• European Presence: Cloudmark's filtering is also present across European providers such as Tiscali.it, Libero.it, TalkTalk.co.uk, and Bluewin.ch.
• Dynamic Usage: The specific anti-spam solutions adopted by MBPs can change. For instance, Comcast has transitioned from Cloudmark to Vade for some of its filtering.
• Synacor's Role: Some internet service providers (ISPs) like CenturyLink (Embarq) and others might utilize Synacor, which could potentially layer Cloudmark's solutions.
• Filtering Layers: Spam filtering is not solely reliant on one solution; MBPs often employ multiple layers, including internal blocklists, even when using Cloudmark.

Key considerations

• Deliverability Impact: Being identified as spam by Cloudmark can significantly impact deliverability to affected MBPs, potentially leading to emails being blocked or routed to the junk folder. This underscores the importance of proper sender authentication and reputation management.
• MX Record Analysis: One way to identify if a domain uses Cloudmark's full cloud-hosted solution is by checking if its Mail Exchange (MX) records point to *.cloudfilter.net. This offers a clear indicator of their filtering infrastructure.
• Non-Deterministic Filtering: Even if Cloudmark flags an email as spam, it does not guarantee spam folder placement. MBPs use a complex array of signals for inbox placement, as discussed in our guide on how mailbox providers perform individual level filtering.
• Proactive Management: Senders must continuously monitor their deliverability and be prepared to contact mailbox providers if they notice issues, especially with providers known to use Cloudmark.

Key opinions

• Specific ISP Inquiries: Marketers frequently inquire about specific ISPs like Spectrum, Comcast, Optimum, and Cox, recalling them as Cloudmark users.
• Impact Assessment: A primary concern is determining the percentage of their master list affected by Cloudmark filtering, highlighting the need for accurate user data regarding provider usage.
• Observation of Filtering: Some marketers observe correlations or similarities in failure messages that lead them to suspect a particular provider uses Cloudmark, even without definitive proof.
• Feedback Loop Importance: The existence of feedback loops from MBPs helps marketers understand and manage spam complaints, which Cloudmark might trigger.

Key considerations

• Accurate Data Needed: Marketers seek accurate, up-to-date lists of MBPs using Cloudmark to better segment their sending and manage reputation, especially given that some providers might change their anti-spam solutions.
• Beyond Content Scans: It is important for marketers to remember that even if a content scanner like Cloudmark flags an email as spam, the final inbox placement decision is influenced by multiple factors, not just content. This is particularly relevant when considering feedback loops and overall deliverability practices.
• Testing and Monitoring: Regular testing and monitoring of deliverability to known Cloudmark-using MBPs can help identify issues quickly. Marketers could use tools such as an email deliverability tester to assist with this.
• Understanding ISP Specifics: Some ISPs, like Cox, might have specific policies such as not allowing new email addresses, which could affect list growth and deliverability strategies.

Key opinions

• Comcast's Transition: While Comcast historically used Cloudmark, an expert confirms they are currently using Vade for some filtering, though older Time Warner Cable (Roadrunner) systems might still use Cloudmark Authority for Email (CMAE).
• Beyond Content Scans: Experts emphasize that a determination of 'spam' by a content scanner like CMAE does not automatically lead to spam folder placement, indicating other filtering factors are at play.
• Identifying Cloudmark Usage: A definitive indicator for Cloudmark's full cloud-hosted solution is when an ISP's MX records include *.cloudfilter.net. Additionally, analysis strings within email headers can confirm usage.
• European ISP Use: Experts also point out that Cloudmark filtering extends to European providers such as Tiscali.it, Libero.it, TalkTalk.co.uk, and Bluewin.ch, showing its global reach.
• Synacor Partnership: There is a general impression that Synacor (used by providers like CenturyLink) may also incorporate Cloudmark technology, possibly with more aggressive filtering.

Key considerations

• Header Analysis: Analyzing email headers from problematic domains can help confirm which spam filters, including Cloudmark, are in use. This method provides concrete evidence for troubleshooting deliverability issues.
• ISP-Specific Knowledge: Due to the dynamic nature of ISP filtering, direct communication or access to ISP-specific information is often needed for precise details on their anti-spam setups. This is relevant to questions like whether Apple uses Proofpoint or Cloudmark.
• Complex Filtering Ecosystem: The email filtering landscape is complex, with providers often using a combination of external services (like Cloudmark) and internal blocklist management, as documented in guides like Mailbox Providers 101.
• Continuous Monitoring: Given that filtering setups can change, senders should continuously monitor their blocklist status and deliverability to adapt strategies accordingly.

Key findings

• Carrier-Grade Filtering: Cloudmark offers a carrier-grade content filtering engine, known as Cloudmark Authority, designed to block spam, phishing, and malware across various messaging streams, including email, SMS, and MMS. This is explicitly stated in their documentation on email messaging security.
• High Accuracy: Cloudmark Authority boasts greater than 99% accuracy in blocking unwanted messages with near-zero false positives, a critical feature for large-scale MBP operations.
• Comprehensive Protection: Their solutions provide anti-spam, anti-phishing, and anti-virus filtering, forming a comprehensive security layer for messaging infrastructures.
• Service Provider Focus: Cloudmark explicitly targets Internet Service Providers (ISPs) and mobile carriers as their primary clients, indicating their systems are built for high-volume, complex environments.
• Integration with BIMI: Cloudmark can support technologies like BIMI implementations by mailbox providers, enhancing visual brand recognition and trust.

Key considerations

• Network Level Filtering: Cloudmark's solutions operate at a carrier-grade level, meaning they are deployed directly within the infrastructure of large service providers, filtering vast amounts of traffic before it reaches end-users.
• Real-time Threat Detection: The technology leverages global threat intelligence to provide real-time protection against emerging threats, crucial for the dynamic nature of spam and malware.
• Impact on Deliverability: Senders to MBPs using Cloudmark must ensure their email practices align with industry best practices to avoid being flagged by such highly accurate and pervasive systems. Understanding which Mail Transfer Agents (MTAs) are in use can also be helpful.
• Messaging Stream Coverage: Its ability to protect multiple messaging streams highlights its versatility and widespread use beyond just email, offering a holistic security approach for carriers.