The company I work for maintains it's own email servers, and I rarely need to go out side the system. Only a few times per month. In the last three years I only receiveed two juck e-mails.
My account at home only accepts know senders.
You can avoid unwanted e-mails.
Yup. Good spam filters are a must though unless you change email addresses often. I have had the same email address for more than ten years now. Not only that, but my primary is just my initials, so I get hit with every automatic address generating spambot on the planet. Prior to moving to some extremely powerful filters at my email provider, I was getting 200 or so spam a day, and had created filters that were basically whitelists. If you weren't on the list, you got dumped to trash.
I support the author's idea of requiring computation be a part of generating the email, but see issues with this when it is applied to some of the mailing lists I'm on that have been ongoing concerns for years. I also don't much care for a system that will do away with anonymous email, as there is a place for even such things.
I've tried to encourage folks to use encryption for years, but have pretty much given up that battle, because people just don't care, even when they should.