> What would you suggest to replace e-mail while retaining its flexibility?
There’s no reason why we cannot redesign the email paradigm around a totally new protocol. The problem isn’t that’s it’s technically difficult, it’s that SMTP is too prevalent now. It would take someone like Google abusing their market share so bring in a successor.
Also any replacement would need to be at a protocol level. A lot of the attempts I’ve seen have also tried to modernise the experience as well (like Google Wave) but the reason email is successful is because it is familiar.
Granted it's already nicer for clients not to need to configure SMTP to begin with.
Acessing port 25 of server is usually blocked by ISPs as a way to prevent spam.
Authentication with mail is separate, usually to allow for relaying whilst anyone can usually drop emails IFF your server is the destination.
Confusing and needlessly complex? Yep. Natural result as of uncontrolled evolution? Yep.