My spam filter works very reliably for all such cases; my first and only manual rule I had to add recently was to stop "bitcoin" spam delivered by Jira accounts; and I also check the filtered messages from time to time. I think there will be spam with any protocol we might get in future.
Yes, but it's kind of anticlimactic isn't it? If the issue was SMTP/protocol, then spam within the gmail network wouldn't exist. But it's not the case.
The main issue is that email is designed to accept messages from strangers you don't know. Because you want that, and it's a core feature. You will have spam on any network where there this is possible.
If you remove the ability to being contacted from strangers, then email would stop being useful.
You don't even need to change the protocol if you wanted zero spam.
I have one email address where I accept only PGP-signed messages I trust with my known keychain, and discard everything else. I can publish this address anywhere. No spam gets through. There are a couple of other ways you could do this with fancy header tagging if you really wanted to, it's besides the point. The issue goes away as soon as you ignore the first contact problem.
