It's up to you to encrypt your data. If any service says that they will encrypt your data at both ends, then you are trusting their processes.
Also, beware about your devices. There was a judge led inquiry in the UK some years ago; testimony from a former government employee in the private sector was along that lines of "we can only install software on your computer if you open the attachment, but emails from a government agency can run the code even if you︀ don't click the attachment".
Android, Iphone, Windows, whatever. That's not paranoia. It's acknowledgement that when︁ the finest minds in cyber security find a backdoor, they don't send an email to︂ The Register, they keep it quiet.