I'm emailing this first because I don't always have good success with
   communication.
   A messaging system is needed with the following properties:
   - sneakernet/airgapped cryptography
   - immutable preservation of public discourse
   - support/preference for anonymity
   - integration with or expansion of one or more systems that are already
   in-use, with one or more existing development and user communities
   - peer to peer, disaster-ready
   - cryptographic delivery (and/or read) receipts
   - simple, clear reimplementable and third-party-maintainable design,
   making heavy reuse of few basic parts
   Although some of the above properties are common, some are very rare.
   The rare properties should be prioritised.