These are sensible ideas, that have mostly been implemented. - IMAP could be improved, but nobody wants to end up with yet another standard... - look at hashca

These are sensible ideas, that have mostly been implemented. - IMAP could be improved, but nobody wants to end up with yet another standard... - look at hashcash, or DKIM plus some reputation system. The big providers - GMail, Yahoo, Hotmail, et al. - run such reputation systems. You can learn more about dealing with those by searching for "deliverability" - GMail is perfectly happy to push a notification to your smartphone, at least. - "Precedence: bulk" exists, as do other headers for more specific situations.