I was thinking primarily for close friends, but for broader contacts, I agree with you, so I was thinking of a system that would allow them to unsubscribe from certain topics (e.g. politics)
How do you unsubscribe from certain topics? Would you have to email your friend and ask him or her to not tell you about politics? There's a whole lot of social pressure that means people are reluctant to do that.
The idea would be that when you send an email, you give it a category, like politics. Then at the bottom of each person's email, there are two links: 1) Unsubscribe from person X's emails about category Y, and 2) Unsubscribe from all of person X's emails from this system
So if that person clicked link #1, the token in the link is verified that it was created for that email address, and then it's noted in a database. In the future, if person X sends another email for that category, it won't go to that person. I'm thinking the sender wouldn't even know that the person unsubscribed
