pep

pretty Easy privacy (p≡p or pEp) was a pluggable data encryption and verification system that provided automatic cryptographic key management through a set of libraries for written digital communications.
It existed as a plugin for Microsoft Outlook and Mozilla Thunderbird as well as a mobile app for Android and iOS. p≡p also worked under Microsoft Windows, Unix-like and Mac OS X operating systems. Its cryptographic functionality was handled by an open-source p≡p engine relying on already existing cryptographic implementations in software like GnuPG, a modified version of netpgp (used only in iOS), and (as of p≡p v2.0) GNUnet.
pretty Easy privacy was first released in 2016. It is a free and open-source software.
p≡p was advertised as being easy to install, use, and understand. p≡p did not depend on any specific platform, message transport system (SMS, email, XMPP, etc.), or centrally provided client–server or "cloud" infrastructures; p≡p is fully peer-to-peer by design.Keys are exchanged opportunistically by transferring via email.

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