@lanodan sure, we are depending currently on SMTP and IMAP for sending and receiving messages. But the email system is not exhaustively described by it. There have been many transports, for example UUCP (there is an interesting new take called NNCP) or contemporarily the Hermes project which uses long range radio specific transports in remote rain forest and African regions. There also are r&d directions here wrt onion routed chatmail relays https://github.com/chatmail/relay/issues/487