Tim Streater :
Your world is clearly different from mine. I don't get spam of the sort you describe. I haven't received anything remotely like the message that started this thread, or dick enhancers, or Swiss watches, etc, for many many years.
Examples of the spam I get are shops that I've bought from wanting me to know about their latest offers, or friends inviting me to sponsor them running a marathon etc. They do that once, I ask them to stop, they don't do it again.
There is no classic spam filtering at my ISP[1], as far as I'm aware, or in my mail client. I guess there might be a spam filter at the throwaway gmail address you'll find in the headers of my Usenet postings; I've never bothered to check. I do have my own method of spam control, which boils down to taking care whenever I'm asked to provide my e-mail address.
I don't get cold phone calls either. Or junk e-mail.