Kevin Werbach [Werblog] posted an article on Slate about how spam will kill email as we know it. Its a good summary of how 30% of email is commercial spam, the failures of blacklist approaches and the rise of whitelists.
Blacklist filtering, no matter how the filter is defined (individually, at the server, serviced or collaboratively) will never be fully effective because new circumvention techniques always arise, funded by the economic of spam that favor spammers. Whitelists succeed, but change the nature of email -- it looses the characteristics of an address. The costs of first contact will increase, requiring contact through alternative modes of communication or handshake negotiation that creates personal costs doesn't work with some uses of email. Other solutions, economic and legal have yet to present viable alternatives. Spam is 2002's biggest consumer leaky pipe, the arms race is on and polution costs will only escalate.
That said, even if total solutions don't exist, existing ones provide value. Each solution is more appropriate for different segments. I believe MailFrontier's whole product concept approach may be the best for a spamming company and may be the winner in the latest investment bubble. Im using Brightmail's private labeled service, Earthlink's Spaminator. A serviced blacklist approach, its about 95% effective with no false positives, which works for me. For now.
But let me draw your attention to a bigger problem than commercial spam -- Occupational Spam. Its the unwanted or uncessary email that clogs corporate mail systems, characterized by excessive CC'ing. Gartner and others estimate Occupational Spam to be 30% of email volume. The problem grows at pace with email, at 30% CAGR.
What's worse -- filter-based solutions do not work to solve this problem. Email sent by an employee to another cannot tolerate false positives and must at least be skimmed. This creates tremendous time costs relative to commercial spam.
According to Business Professor Catherine Cavanaugh, "It's a management issue, if you're getting 50 or more emails a day, you're spending four hours a day just doing email. That means it's no longer a productivity tool." Quantify this with the average fully loaded cost of an employee and multiply it by 10,000 employees -- and you have a really big problem.
Occupational Spam is a larger problem than commercial spam. Both increasingly create costs that will drive adoption of other modes of communication. And what's worse is we are all loosing time.