Some have argued that we can address the spam problem by redesigning SMTP, the basic email-handling protocol used on the Net. Eric Rescorla rebuts that argument with a clear and cogent explanation of why the real problems lie elsewhere. Required reading for those who want to understand what can be done about spam.
The case for replacing SMTP (which Eric rebuts) reflects a general fallacy about the Internet. The fallacy goes like this: the Internet was not originally designed with security in mind; the Internet as designed fails to provide some desired security guarantee; therefore if we redesign the Internet we can achieve the desired guarantee. The error, of course, is in the hidden assumption that the desired guarantee is achievable at all. In the case of spam, there doesn’t seem to be a technical solution.