"SMTP has outlived its usefulness" (was: Forwarding services)

As per up-thread, even with Internet shut-off, there's still packet radios in everyone's pocket for short-distance mesh networking, and LoRaWAN is also wide-spread and can't be banned cause it gets some use in industry and agriculture (e.g. for sensors). LWN has had stories before on Free Software systems to setup well-featured messaging systems on those short and mid range packet radio systems.

There is also a massive cost to shutting off the Internet. You can't be a modern country with no Internet. It won't stay shut off for long (as we're seeing in your example).