Still in beta, but worth to check and try. I think Nadim is making a great job to make secure communication tools very easy to use. https://www.peerio.com/
Peerio: Privacy for Everyone. https://www.youtube.com/watch?v=e01qNS4koTs Again, more "zero knowledge" or "we can't get into your stuff" services, the better.
No, I'm serious. That's the trend or even bare minimum standard now. Especially when compared to say Dropbox which all your files are readable by anyone. http://www.zdnet.com/article/after-snowden-slams-dropbox-twice-ceo-responds-its-a-trade-off/
Thank you, Veeshush, for posting the additional clarification! All btw, looks like it's going to be a gorgeous, sun-shiny day. Bon jour.
Apparently, the founder Nadim Kobeissi has disagreements with the current owners of Peerio, and they threatened to sue him for making the details public. https://twitter.com/kaepora/status/636254431911260160