D E M S
The idea of the project is as follows: the Ethereum blockchain stores encrypted messages. You have a private and public key (not from your Ethereum wallet, but new ones generated). The messenger encrypts your message so that only the recipient can read it (even you can not, so you should not to clear the local storage of the browser). Then this encrypted message is sent to the Ethereum blockchain. The recipient is notified. You do not need to be online! The message will be delivered, even if the recipient comes in a year.
Moreover, for greater anonymity you can constantly switch accounts in metamask, your address in the messenger does not change.
Try this messenger: https://cryptocurs.github.io/dems/
Community: https://twitter.com/dmint18
Contract: https://etherscan.io/address/0xa4989f68324f3a152e05bd9b11098425b927652b#code
More information: https://medium.com/@smint2018/decentralized-messenger-dems-how-it-works-40ce4e7691a4