S/MIME

S/MIME (Secure/Multipurpose Internet Mail Extensions) is a standard for public key encryption and signing of MIME data. S/MIME was originally developed by RSA Data Security Inc. S/MIME functionality is built into the majority of modern email software and interoperates between them.

Protocols
Anonymity
I2P
Tor
Communication
DNS
IRC
Matrix
SIP
Tox
XMPP
Encryption
GPG
OMEMO
OTR
S/MIME
SSL/TLS
ZRTP
Synchronization
ActiveSync
CalDAV
CardDAV
WebDAV
Syndication
RSS