About 5 years ago an ex USMC officer who was lecturing (in a non-secret subject) at a major US Uni. told me they told their students to remember than ANYTHING you commit to writing on a PC/phone/Tablet can longer be considered secret or confidential - especially emails
Like it or not we live in a Surveillance Society - sometimes that's good and sometime's that's bad but it is what it is and there is no turning the clock back.
The only answer is to do what the SVR were apparently doing in Moscow - buying a lot of steam driven typewriters................. but then maybe they were on special..........