Mozilla Thunderbird 78 is a major release of the most widely used open-source and multi-platform email client that brings numerous new features, an enhanced user interface, and dozens of other improvements for a modern email experience. One of the highlights of the Thunderbird 78 release is the inclusion of OpenPGP functionality, which lets you send encrypted emails without having to rely on a third-party add-on like Enigmail or Autocrypt. That’s why Mozilla warns Enigmail users to not update to Thunderbird 78 at this time.