There is no shortage of startups and enterprises animated by, or outright proclaiming, replacing e-mail as the de-facto open internet messaging standard. VC Investors are forever fascinated by funding such endeavours. #matrix #simplex #slack etc are examples.
#deltachat endorses e-mail but reconfigures and repurposes it to serve for interoperable instant messaging. The #chatmail server network relays end to end encrypted e-mail only, and servers are reduced to dumb store-and-forward relays.