An electronic message transport protocol applies two distinct sub-protocols, a message transport protocol and an encryption key management protocol, which operate in tandem to provide enhanced security. The protocol may employ an existing SMTP infrastructure to transport secure email messages, and a key server implementing the key management protocol to transport key packets associated with the secure email message. However, the protocol need not be limited to email, and may be applicable to other electronic message applications. The message transport protocol permits communicating parties to obscure their identities to enhance security. The key management protocol supports message security, and allows senders to control access to messages even after they have been transmitted. The message transport protocol permits the sender to encrypt the entire message and utilizes the key management protocol for exchange of necessary keys. The message transport protocol relies on a group addressing scheme to obscure individual sender and recipient identities.