Ask HN: Why isn't whitelist only email used more often or even the standard?
I've been thinking about whitelist only email for personal though. Why isn't that more of a thing? You can definitely do it with existing services, but this could already be a standard and hosted independently.
You could give people a portal where they can make a request to send you emails and you can approve it and revoke that approval at any time. You can generate keys for people so they'll be whitelisted when they've signed up. You could even print those on business cards and tie their usage to events. You could use that to provide a more complete identity for contact. Chats, currency wallets, feeds of information you're publishing, but you'd never have to deal with an open connection to stuff you did not want.
When I search the problem it appears as if this idea doesn't have any traction anywhere. I had my own email server on Slicehost in like 2001 and haven't messed with operating my own since GHA came online. I am not an expert in this area. What am I missing?