My client doesn’t want to send sensitive documents around by email and I understand this - as many of his coworkers roam the world using free and unencrypted WiFi at hotels and airports. So I recommended him sharing everything as Libre Office Online documents and send the links instead which is really nice. (as you can revoke it later and you can protect the document with a password either)
But it is still a media breach to send anything off via mail. Social sharing i.e. sends the NC link by email for the reciever to open in Libre Office Online.
Unfortunately Social Sharing Email is a mere mailto which doesn’t even work properly with me - nor would it with some worker in the field. How about sharing with the official mail-app or (a dream) via RainLoop.
For me a a consultant/admin it is important to have as least as possible dependencies at the endpoint as the company i’m consulting is a loose bunch of non-IT freelancers bringing their own devices. Any ideas how to solve it?
For the time beeing: Share by Link, copy the link, open Rainloop, paste the link, write a nice cover letter, send it off… Many pitfalls for the technically challenged. 
PS: and if done so in an Internet Café: the link would be still the clipboard for the next person to open the document with.