Guaranteed protection of digital data is a primary duty of every company and government administration. DEFINITION BS Mail is a hybrid post-quantum application for exchanging encrypted digital messages and files. The application allows sharing and playback of protected multimedia content, alternative anti-spam protection, and many more. BS Mail provides users with a high degree of anonymization and the ability to work simultaneously with multiple mail servers. The application provides excellent opportunities for testing secure mobile solutions and building an attractive design. The application allows the following actions: • Encrypting or decrypting incoming and outgoing electronic messages; • Encrypting content and attachments; • Hybrid mechanism for managing user passwords; • Managing the cryptographic primitives used; • Storing system information in secure electronic notebooks; • Recording critical information in implicit form; • Managing cryptographic processes; • Using multiple mail servers; • Alternative anti-spam protection; • Experimental conduct of digital marketing; • Rapid destruction of used critical information; • Automatic control of incoming and outgoing processes; • Content control, etc.