Whiteout.io is a chrome app for email, plus an android app with key-synch between the two. It's still early stages, so it has some issues (like indexing all your emails, since forever, and overheating your computer). But it's very promising.

Most people want to continue using webmail though. That's why Mailvelope is so awesome. Continue using webmail, but just have an extra button added which opens up an editor with a bit "encrypt" button. Pretty easy, and pretty safe.

Mutt and Thunderbird come to mind.