Cloudmark claims to protect about one billion subscribers for the world's largest carrier networks, including over 75 percent of all major service providers in the United States and Japan. Its client reference list includes: Cablevision, Comcast, Cox Communications, EarthLink, Reliance Connects, Swisscom, Tele2, XS4ALL (KPN), as well as social networkings companies MySpace  and probably Facebook 
Cloudmark sits on the board of directors of the Messaging Anti-Abuse Working Group, and the steering committee of the Anti-Phishing Working Group, it also teams with Sendmail, Habeas, IBM, ReturnPath and Yahoo!.
In 2005, company hired few franchisee worldwide for launching there anti-spam and anti-phishing products, among which SynapseIndia targeted 50,000 mailboxes in one quarter. In February 2010, Cloudmark acquired Bizanga Ltd., the developer of a message processing platform.
Cloudmark claims to be "a comprehensive global sender monitoring and analysis system that delivers timely and accurate reputation on good, bad, and suspect senders." Cloudmark provides an extensive overview of the approach it uses to make various determinations of "reputation" quality. Spam filtering is collaborative. Cloudmark users practically "vote" what’s spam and what not. The method is known as Vipul's Razor.
However, Cloudmark does not disclose which specific criteria was applied in its determination of “reputation” quality related to a discrete email sender. Nor does Cloudmark make available a discrete list of email senders which are subject to an adverse reputation determination. Many other providers of reputation assessments do have this facility. As a result, the administrators of a Cloudmark blocked email server have no opportunity to determine whether or not Cloudmark may have unjustly assigned a less than acceptable reputation to the email server.
In process, once an adverse determination is assigned to a sending email server by Cloudmark, the entire stream of email sent from it to a server, which applies Cloudmark's reputation assessment to its email acceptance rules, results in all such email being persistently blocked from delivery. A generic message is delivered back to the sending server each time that a transmission to a Cloudmark designated recipient was refused. The specific reason for the refused delivery is not disclosed. The intended recipient is not notified that all email from a certain mail server is being persistently blocked. Such may indeed have an adverse impact on time sensitive legitimate email messages which are being blocked without notice to the intended recipient. However this process is true for almost every reputation-based services where their usage and possible effects on non-spam mail delivery are completely the same as of Cloudmark while the methods being used to evaluate the reputation are different.
Cloudmark does provide a link to an on-line form to potentially “reset” [remove the blocking mechanism], subject to Cloudmark's review process and approval. However, it can take up to 48 hours for the block to be removed.
- Patrick Hoge (2010-02-17). "Cloudmark to buy Bizanga". San Francisco Business Times. Retrieved 2010-05-28.
- Robin Wauters (2010-03-03). "Messaging Security Company Cloudmark Raises $23 Million From Nokia, Others". TechCrunch. Retrieved 2010-05-30.
- Brad Stone (2010-11-18). "Dear E-Mail: Die Already. Love, Facebook". Bloomberg Businessweek. Retrieved 2010-02-05.
- Chris Anderson (writer) (2002-09-01). "Spam-Haters of the World Unite!". Wired (magazine). Retrieved 2009-10-25.
- Robert Haskins (2005-03-11). "Interview with Vipul Ved Prakash". ISPadmin. USENIX. Retrieved 2009-10-25.
- Brenda Ropoulos (2006-06-26). "Cloudmark Stops Viruses Before They're Even Named". Press release from Cloudmark, Inc. OpenPR. Retrieved 2009-10-25.
- Stefanie Olsen (2003-11-02). "Sendmail, Cloudmark team against spam". CNET. Retrieved 2009-10-25.
- Mickey Alam Khan (2008-02-20). "Habeas, Cloudmark partner for certified mobile email delivery". Mobile Marketer. Retrieved 2009-10-25.
- Keith R Hutchinson (2009-05-25). "Cloudmark and IBM BladeCenter". IBM Corporation. Retrieved 2009-10-25.
- Ken Magill (2008-01-29). "Yahoo!, Cloudmark Implement Return Path Certification Scheme". DIRECT. Retrieved 2009-10-25.
- Franchisee Hired