GPG is the classic solution to encrypted email, but it has some challenges that make it less likely to enter common usage. The primary interface is command line

GPG is the classic solution to encrypted email, but it has some challenges that make it less likely to enter common usage. The primary interface is command line and confusing, though there are a few good GUIs for it, including GPGTools for OS X. GPGTools also interfaces elegantly with Mail.app. The bigger challenge is secure key exchange. You either need to exchange your public keys in person, or use a difficult to manipulate approach to verifying them, e.g. exchanging keys via unencrypted email and then calling each other to verify each other's key fingerprint over voice communication to ensure the keys were not MITMed in transit. If I could, I'd encrypt everything, just as a matter of principle. Even if it doesn't technically matter if it gets intercepted, encrypting all your communications is a good way to regain the privacy the government is saying we no longer have any right to. In practice, I'm not going to be able to encrypt everything, because few people are willing to use GPG yet, and that limits my ability to use it as well. But I'll do so when I can, and encourage others to use it.