An electronic signature and message encryption are implemented in MyOffice Mail with support for Russian crypto-algorithms. These features are also available for Linux and Windows mail clients, in the cloud services, and in the mobile apps for Android and iOS.
To work with electronic signatures and encryption in these products, any qualified certificates covered by Federal Law of Russian Federation No 63-FZ RF will suffice.
To fully implement the electronic signature and message encryption functionality, you will have to purchase CryptoPRO CSP software. Licenses are available at the licensing centers and CryptoPRO dealers: https://www.cryptopro.ru/dealers