The contents of an e-mail is sent in clear text through a multitutude of internet servers. On each of these, as well as in transfer between them, the e-mail is readable, even changeble, so neither confidentiality nor authenticity is guaranted on arrival.
I configure your software, help you to generate your "private / public key" and teach you to employ it. The installation is on your PC, laptop, smartphone and/or USB key.
With the USB solution, your emails always thereby and you can view her on each computer. In addition, the configuration of your email client and your contacts will be the same everywhere