ciphermail
Ciphermail email encryption gateway (S/MIME, OpenPGP, PDF encryption)
is a standards based centrally managed email server (MTA) that encrypts and decrypts your incoming and outgoing email at the gateway level. Ciphermail Email Encryption Gateway is compatible with any existing email infrastructure like Microsoft Exchange and Lotus Notes and has support for S/MIME, OpenPGP and PDF encryption.
Ciphermail Email Encryption Gateway has a built-in CA which can be used to issue X.509 certificates for internal and external users.
For additional security, keys can...