Paul Graham, the head behind Lisp, tackling spam in an all-interesting essay from 2002:
I don’t know enough about the infrastructure that spammers use to know how hard it would be to make the headers look innocent, but my guess is that it would be even harder than making the message look innocent. Assuming they could solve the problem of the headers, the spam of the future will probably look something like this:
Hey there. Thought you should check out the following:
http://www.27meg.com/foo