Mailvelope

Mailvelope is a Chrome extension that enhances your email provider with end-to-end encryption. With support for common webmail providers like Gmail, Outlook.com, and Yahoo!, Mailvelope adds missing encryption and decryption features to your email interface. It uses the PGP encryption standard (OpenPGP, GPG) and is compatible with other PGP applications. You can also encrypt files on your hard drive and send encrypted email attachments. Mailvelope is open-source, based on OpenPGP.js, and seamlessly integrates security into your workflow.