Earlier quoted context omitted.
While I understand your sentiment, I respectfully disagree that it does not matter if it's a smart idea. Because if it is not a smart idea then that means we can do better. One of the projects I'm working on solves the "closed ecosystem" problem. The use of the term "closed ecosystem" is ironic because it seems to me that the "open" nature of email receiving (not sending) is what leads to the spam problem. In other w…
"Consider the idea of running a mailserver than only accepts mail from a predetermined set of sending addresses." How is this functionally any different then blacklists? That's just a whitelist instead. So instead of new mail severs "quite likely" being on a blacklist, they are definitely not going to be on a whitelist. And no, it doesn't matter if isn't a smart idea when you aren't in a position to change anything.…
I'm afraid there's no need to convince any provider of anything. At this point, Alice and Bob are sending and receiving email without the need for any third party "email provider".
Functionally blacklists and whitelists are the same. They both have the same goal. But they are not the same in their effect. Blacklisting an entire netblock to stop one bad IP address affects many IP addresses who do not need to be blocked. Whitelisting a single known IP address does not have that side effect. For Alice and Bob, handling their own messages may be a desired option. Of course, not everyone may follow Alice and Bob's example. But who cares? The population using email is enormous and diverse. The point is that if someone wants a better solution than what "email providers" offer, she can get it.