We\u2019ve all heard that spam is in the eye of the beholder - what might be spam to you is valuable content to someone else. As a result, spam blocking, particularly in a large enterprise, can be problematic because there is a wide diversity of views on what constitutes spam.To address this problem, many spam-blocking products employ personal whitelists, blacklists and other technologies, allowing individual users to custom spam-blocking to their specific needs.Recently, Cloudmark announced Immunity, a technology that the company claims will block 100% of spam without generating false positives. Immunity uses a technique that Cloudmark calls Email Genetic Mapping (EGM), an artificial-intelligence-like technology that learns what spam is and is not based on the behavior of the enterprise as a whole, departments within that enterprise and individual users. Administrators can control what the enterprise considers spam, while individual users can provide feedback to further tune the system and increase its accuracy. Immunity employs a visualization technology that allows administrators to delve into the inner workings of Immunity, providing them with a valuable analysis tool that allows optimization of the system.There are a number of very good spam-blocking systems on the market that can block 95% or more of the spam entering an enterprise while generating few false positives. However, Cloudmark\u2019s claims of 100% spam-capture efficiency and zero false positives are certainly bold claims.While beta testing has shown excellent results thus far in terms of the percentage of spam captured, the ability to generate zero false positives should prove difficult to achieve. This is not because of an inability of Immunity or other spam-blocking products, but because users\u2019 perceptions of false positives can change rapidly. For example, Amazon.com has reported that a user can request a statement from the company, receive it a short time later and then complain to the company about Amazon sending them spam. That\u2019s probably not an uncommon scenario among publishers of newsletters and other opt-in content.It will be interesting to see empirical results from actual Immunity users after the product is released in July. Pricing for Immunity will be $15 per user per year.