Bitmessage is a P2P communications protocol which is used to send encrypted messages to another person or to many subscribers. It is decentralized and trustless, meaning that you need-not inherently trust any entities, like root certificate authorities. It also aims to hide “non-content” data, like the sender and receiver of messages, from eavesdroppers.
Here is the whitepaper!
The program is in Beta so feedback is appreciated.