> uprooting a fundamental protocol and replacing it with something else isn't an easy task to do on a network as big as the Internet It's a bit of work, but re

> uprooting a fundamental protocol and replacing it with something else isn't an easy task to do on a network as big as the Internet It's a bit of work, but relatively straightforward if anyone really cares about it enough to spend effort on it. Add a new message to the SMTP protocol that says "I have mail for you, but I'll only give you the headers right now. When the user opens it, you can call me back and ask for the content." If the target server doesn't understand the message, fall back to allowing the email to be recalled by implementing a delay. Publish an informal protocol spec before you publicly release any code; try to get it accepted as an RFC. Create an open-source reference implementation for the most popular open-source email programs -- mail servers, mail clients, webmail platforms. Get it accepted in the upstream of those projects. As people start using it, they realize it's really good and start to demand it of commercial implementations. As there's a published spec, the commercial implementations end up being mostly compatible with each other and the open-source work.