You argue against block listing, but then suggest blocking the entire Internet except the few people you want to send you email.
You say that only people who you have given your email address to should be able to send you email, and then you say there should be a lookup system to get email addresses. (But what's the point of the email directory system if you can't send email to someone because they haven't white listed you yet?)
> but I don't receive important email from all that many different people.
Eh, depending what you mean by "important" I do receive a lot of important email from lots of different people. My email addresses have been used on the public Internet for many years, and I've had a lot of communication to those email addresses, and those communications have brought me great joy. And I also have a variety of people who email me about work related stuff - I won't have prior knowledge of those people.
I think I'm missing something about your system. Please, is it something that you already have well planed out? (Even if not in a state that can be deployed yet) Or is this something that you've just started thinking about?
So long as you're not suggesting Challenge Response we can have a discussion about it.