'Create an instance of an ESMTP server protocol.
@type addr: L{IAddress <twisted.internet.interfaces.IAddress>} provider
@param addr: The address of the ESMTP client.
@rtype: L{ESMTP}
@return: An ESMTP protocol.'

def buildProtocol(self, addr):

    p = SMTPFactory.buildProtocol(self, addr)
    p.challengers = self.challengers
    p.ctx = self.context
    return p
