[kwlug-disc] Secure email alternative

[Paul Nijjar]

I am looking for the following communications platform: 

- Allows asynchronous communications, like email.
- Is based on a client-server model, with clients for multiple
  platforms (Windows, Linux, Mac OS X) and a server that is FLOSS and
  installable on Linux.
- Requires registration to use (preferably by submitting a public SSH
  key).
- Does NOT have a web client or web interface.
- If the server requires opening a port on the Internet, the
  communications to that port should be authenticated and preferably
  encrypted.

I do NOT want email with GPG or S/MIME or whatever. The service does
NOT need to be federated. I am indifferent whether whether the data is
encrypted on the server so that sysadmins cannot snoop on it.

Yes, I understand that this is an odd set of requirements. Does such a
thing exist already? I am not sure what search terms to use. 

- Paul 

-- 
http://pnijjar.freeshell.org