The idea is that simple..

I am sure that someone can correct me on a point however there is US legislation that states something about using that exact combination of words that makes apparent spam, not spam.

The spammers get around the laws by using that set of words. Thats why I say, you got to love the Americans - they introduced a set of Laws about labelling things that makes picking up spam very easy. You got what I meant wrong Andy - sorry about that mate.

It appears there is difficulty believing the fact that zero spam is the case actually surprises me. What, conceptually, is difficult about understanding the fundamental principle of a very low tech solution to a high tech problem