With YMOZ, you cna use the same OpenPGP.js libraries maintained by ProtonMail to exchange emails securely using PGP encryption. SOGo supports S/MIME email signing and encryption. When receiving S/MIME signed emails, SOGo automatically extracts the PKCS (Public-Key Cryptography Standard) #7 signature and stores it in the user’s personal address book for the contact associated to the email address of the email’s sender. This certificate will allow the user to send encrypted emails to these recipients.