Cracking the Inbox Code: Cloudmark

Marketo Employee
Marketo Employee

Cloudmark is a secure email gateway that uses fingerprinting technology to block spam.  Cloudmark has a broad footprint of networks who leverage their technology including:  small and international ISPs, mobile operators, hosting providers and registrars in 165 countries. Customers include EarthLink, Comcast, Cablevision, Time Warner, AT&T, Virgin Mobile, Sprint, British Telecom, Swisscom, Antel, QQ,, WebCentral and many others.  There are more than 1.5 billion mailboxes that may be impacted by Cloudmark filtering globally.


All messages seen by Cloudmark are fingerprinted, and then are deemed 'spammy' or 'legit' based on feedback from the network.  There are three main components of the filtering technology:

  1. Global Threat Network a reputation network made up of ISP abuse teams, system administrators, webmail end-users, desktop users and honeypot spam trap networks.
  2. Advanced Message Fingerprinting real-time algorithms that create fingerprints, or hashes, of various components of an email header, body and other characteristics.
  3. Cloudmark Services and Trust Evaluation System – a complex and highly dynamic system that collects, analyzes and classifies fingerprints received through its Global Threat Network.


The primary drivers of spammy fingerprinting include hitting spam traps or generating spam complaints within the network.  Practices that are likely contributors to spammy fingerprint dispositions include:

  • Mailing to third-party sourced leads (acquired through list rental/purchase/append)
  • Mailing to inactive users
  • Distributing content across large numbers of IPs and providers
  • Affiliate programs that abuse your content or domain


If you feel that you are being impacted by the Cloudmark blacklist please reach out to Support or follow some of our standard recommendations:


Blacklist Remediation (comprehensive)

Simple Blacklist Remediation

Successful Reconfirmation

A Creative Re-Engagement Email Campaign


Thank you Carmi Lopez-Jones for helping craft this post!

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