>>1028324
Make it mandatory for business emails to the customer side (newsletters, delivery notifications, registration emails, customer feedback, amazon, google, apple etc.). 2 years later everyone knows basic usage and proprietary software has to implement it in a way that is usable for everyone. Countries have to host distributed keyservers that keep in sync with each other monthly (to provide their side of by-law privacy protection for their citizens).
Downsides: NPCs will complain that they don't want privacy, because it means cognitive load - and easier to use means better. Companies will complain that privacy costs them money for infrastructure and development - and that's all they care about. No global solution possible, but once anglo-american countries, EU (law still has to be made into national law by each country in the years following) and China have done it - the rest will have to follow suit.
>>1028343
I've also already seen hushmail being recommended. It's hard to know who to trust and as these companies should care a lot about PR, it should usually be not easy to find "dirt".