The use of any "SECURE" e-mail is highly suspect. I use encrypted e-mail for PRIVACY against advertisers , not even close to assuming that anything available to me is "SECURE". The hardware is not manufactured under my control, the operating systems are downloaded from sources I do not control and etc. Bandwidth online is so broad that THEY(tm) could download keyboard captures and screen shots from my computer all day long, and I probably would not notice. I went to 'privacy systems' when targeted advertising began hitting my mail , reflecting interests of my friend on the other end of the Yahoo mail link. He was getting advertisements for chickens and I was getting them for handgun competitions... I had hens at the time and he had been a competition shooter in times past.
In short, if you require SECURE , don't use anything with a microprocessor in it, as a start.
- Sir John Honeybucket