If your ssh public key is published somewhere accessible, it enables someone to spin up an OpenBSD VPS, add your key to the approved keys list, get you the ip, and you can all ssh in and use the internal mail to talk back and forth.
With the files never leaving the server. A tool for more serious times. 

 Bookmarkid 

 I wish I know how to do that. It sounds much more interesting.  

 Try #Deltachat with a personal or trusted mail server.