Apps with 'S/MIME support' feature
Mutt is a small but very powerful text-based mail client for Unix operating systems.
MsgSafe.io provides private, encrypted, online communication with layers of security you can trust.
Email Encryption. Encrypt your emails with GnuPG, OpenPGP, S/MIME or your favourite email client. Keep your secret keys secure on your Nitrokey.No screenshots yet
SMBMail is a groupware server built with a focus on scalability and open standards. It provides secure, enterprise-style email, calendar & collaboration without the high cost.No screenshots yet