We regularly get email from genuine companies, who have collected our email address from somewhere. The worst place for this is the local Chamber of Commerce, who seem only to exist to sell your information on. Despite many requests, they still give out our email addresses.
So if I sent you a link to this page, it is probably because you sent me un-solicited mail and I am explaining why I will NEVER buy from you...
If I am interested in your product, I will contact you. If you choose to fill my email account with un-solicited email, I will buy from someone else first, regardless of where you got my email address from.
Semi-respectable companies who have spammed me, and I will never buy from:
WebWindows
PlusNet
Smart Support
Iwoca
If you send me un-solicited emails, I will do my level best to ensure I never buy from you, because of your marketing practices.
If you get an email from someone out-of-the-blue, ask yourself if you really wanted their contact. 99.9% of the time the answer is no. The reason for this is that it is most likely an email offering one of the internets' most common "products":
Like the rest of the world, we get these all the time.
The people sending the spam know they are sending rubbish. They are intelligent humans after all. They know that 99% of people will see the email for what it is, and delete it.
The reason they still do this is the other 1%. By sending 2 billion emails, a 1% response means 20 million hits. If 1% of those buy something, that's 200,000 sales (or sets of credit card details to steal).
Results like these are why the spammers continue to do well.