Is there any platform available for Ethereum address 0x1d53.. to message 0xcc23..., and so on? It seems like there would be a lot of demand for something like that, which suggests it exists. Off-chain, I guess. I need it for the pairs in Pseudonym Pairs (source code) to agree on a random video channel over something like https://gotalk.to or https://meet.jit.si.
Ethmail.cc is ordinary email + secp256k1 public-private key accounts, email format
[ETH address]@ethmail.cc. Then there is BitMessage, closer to what I was thinking of, stores encrypted messages publicly but only owner of private key can decrypt a message, https://bitmessage.org/bitmessage.pdf. Ethmessenger.co was built after 6 months of research by Ethereum Foundation Advisors. Status.im almost supports key-to-key messages, the account is controlled by Ethereum accounts, but adds a different identifier than the public key. dChat supports ENS domain names, and is like Status.im controlled by Ethereum accounts, but, does not support key-to-key messaging.