PGP (Pretty Good Privacy) is more than 20 years old technology but is yet not widely adopted. PGP is an open source end-to-end encryption standard to encrypt e-mails, protecting you against companies, governments, or criminals spying on your Internet connection Source http://thehackernews.com/2015/06/facebook-pgp-keys.html
Firstly, this will not protect you from the government. Governments are known for tools they have at there disposal for cracking and getting information they need. The issue with this is, you can use any encryption method you wish, however if you're using Gmail or Outlook or anything ran by a corporation if the government comes a knocking at there door with documents to look at your emails? They will gain access. Google usually will fight and has won in some cases but most of the time it isn't worth the battle.