I m surprised by the resilience of email as a communication channel. We need to extend it to carry notifications and ephemeral messages as well. There's no need to lock up tech behind the gates of google and apple
It's resilient because it's the only service that isn't centrally managed by one company, and anybody can federate and set up an e-mail system that communicates with all the other e-mail systems.
It's the same reason SMS is still around, because it's the only communications tool that can send a message to any cell phone.