Serves the SMTP server on the given port and address.

def serve(self, port=None, address=None):
        """Serves the SMTP server on the given port and address."""
        port = port or self.port
        address = address or self.address

        log.info('Starting SMTP server at {0}:{1}'.format(address, port))

        server = InboxServer(self.collator, (address, port), None)

        try:
            asyncore.loop()
        except KeyboardInterrupt:
            log.info('Cleaning up')