The spam situation could also be better if we had designed into that space. Want to send a single email to a sender that you don't have an existing relationship

The spam situation could also be better if we had designed into that space. Want to send a single email to a sender that you don't have an existing relationship with? Hashcash. Have a web service that sends lots of emails? Get user consent beforehand with e.g. an oauth token to bypass or lower hashcash difficulty.