Add Tutanota (#1094)

README.md

@@ -641,6 +641,7 @@ Any comments, suggestions? [Let us know!](https://github.com/jaywcjlove/awesome-
 * [Postbox](https://www.postbox-inc.com) - Powerful, simple and beautiful email client, need to pay for a license.
 * [Spark](https://sparkmailapp.com/) - Fast email client. For both Mac OS and iOS.![Freeware][Freeware Icon]
 * [ThunderBird](https://www.mozilla.org/en-US/thunderbird/) - Software that makes email easier. ![Freeware][Freeware Icon]
+* [Tutanota](https://tutanota.com/) - Encrypted email focused on security and privacy. [![Open-Source Software][OSS Icon]](https://github.com/tutao/tutanota) ![Freeware][Freeware Icon]
 * [Edison Mail](https://mail.edison.tech/mac) - A customisable, simple, and beautiful email client. ![Freeware][Freeware Icon]
 
 #### File Sharing