Briar releases 'Mailbox' that lets you receive encrypted messages from your contacts while Briar is offline
briarproject.org
Likewise, you can send encrypted messages to contacts who are offline, and the messages will be delivered automatically when your contacts come online.
I hadn't heard of Briar before. How is it? It looks like it works with local mesh networking when an internet connection isn't available. Does that work well? Ad-hoc meshes are my favorite feature from the devices in The Expanse book series. Ever since I read those I've been hoping to see something similar working on real phones on a robust, just-works kinda way.
It works great, but it's probably not the app for everyday use. It syncs via Tor, and if the internet is down, it syncs via WiFi or Bluetooth which means you can communicate even when natural disasters destroyed the infrastructur or in war-torn areas. For these special use cases of journalists, activists or humanitarian aid workers its perfect.
That's an excellent function. I keep Briar on my phone but have ZERO contacts. Never know, right?
If you want to join public forums on Briar, you may find this site interesting.
Edit: The person in the link is not me, just to be clear about that.