As I understand it, an Ethereum account is a public/private key pair.

Is it possible to encrypt a message with the public key (how?) that only the account holder can decrypt it with his private key?

You could establish a forum where you could post such messages, for example to PM an account holder.

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    Sorry, mistook this for a duplicate of How can I sign a piece of data with the private key of an Ethereum address? in first place. But you are asking the other way around, very interesting question and welcome to Ethereum Stack Exchange!
    – q9f
    Commented May 17, 2016 at 9:21
  • Does duplicate look good?
    – eth
    Commented May 17, 2016 at 9:40
  • This should not be mark as a duplicate. The link to the answer is not answering anything but self promote his package! Commented Oct 20, 2021 at 4:08