relay

Aside, this bit that Neil and the team are working on is something I think is the 'next big thing': https://www.ietf.org/archive/id/draft-ietf-jmap-emailpush-01... The next, next big thing would be the Chatmail relays[1] supporting JMAP based servers (right now it's Dovecot) and this new targeted push extension for faster notifications without battery drain on mobile. I can see how the Fastmail mobile client will benefit from this RFC as well (it's already incredibly battery efficient, thanks to the team). [1] https://github.com/chatmail/relay

Take a look at delta.chat Your server can be a traditional email server you set up or one of their optimised devocot, smtp relays: https://github.com/chatmail/relay The clients are great (they have reactions!) there is even a really good app store associated : https://webxdc.org/

Cannot find it now, but that's how it was discussed at the time when chatmail server became a thing. It is also how it is configured in chatmail: https://github.com/chatmail/relay/blob/96a1dbac08441034c5990... https://github.com/chatmail/relay/blob/96a1dbac08441034c5990... You obviously must trust that the server runs this configuration, but you can always run your own chatmail, or regular postfix. (If you don't need "federation" with other mail servers, you don't even need port 25 open). However, you can also configure your app to delete messages from the server sooner.