A new Competitive Enterprise Institute study on spam email surveys the effectiveness of current user-based countermeasures and laws and suggests additional strategies for stopping unwanted emails through legal and technical solutions to help Internet Service Providers (ISPs).
The publisher of Fusion Authority has noted the huge amount of spam that does come through major ISPs, and despite contacting them with each message that comes through (numbering into the hundreds), it is an extremely rare case that anything beyond an automated mail is sent, or that the account of the spammer is actually closed down. An ISP may take action when threatened by a lawsuit, or by someone of a large size, but the little guy, no matter how many messages he processes, will be ignored. However, I think it's worthwhile to look at this study to see what some people think on the topic. It should be noted that an overwhelming majority of the spam that comes in will be from a non-U.S. source, and blocking these is not always an option. For example, CHLLO.NL is a major spam source, especially its subsidiary, A2000.nl. The problem is, CHLLO.NL is a major ISP in the Netherlands, and to block that would mean blocking most mail from the Netherlands.
Spam, That Ill of the ISP: A Reality Check for Legislators (PDF, Competitive Enterprise Institute, May 21, 2003)
Competitive Enterprise Institute Site Executive Summary of Article