The incentives aren&#x27;t aligned right. Every business will still need SMTP to receive email from outsiders, and through that SMTP will come spam. Even if two businesses decide to switch to a better protocol between them, they&#x27;re still running SMTP to reach anyone else.<p>And unless you permit sending a single message to both SMTP and better-than-SMTP recipients without any UI awareness, you&#x27;ve built a product that&#x27;s strictly worse than SMTP for end users.<p>You could add features to email to make a more compelling product, and then kill seamless integration with other SMTP users and still have a better product. (See e.g. Slack. Or Facebook, for personal email.) And then maybe in many many years nobody will want email any more. But that won&#x27;t be quick.