def METHOD_NAME(self, user):
    """
    Create an envelope and a message receiver for the relay queue.
    @type user: L{User}
    @param user: A user.
    @rtype: L{IMessage <smtp.IMessage>}
    @return: A message receiver.
    """
    queue = self.service.queue
    envelopeFile, smtpMessage = queue.createNewMessage()
    with envelopeFile:
        log.msg(f"Queueing mail {str(user.orig)!r} -> {str(user.dest)!r}")
        pickle.dump([str(user.orig), str(user.dest)], envelopeFile)
    return smtpMessage