def max_message_size(self, peer):
return None<EOL>
Return the maximum size (in bytes) for messages from this peer. When
        this method returns an integer, there pymta will check the actual
        message size after the message was received (before the accept_msgdata
        method is called) and will respond with the appropriate error message if
        necessary.
        If you return None, no size limit will be enforced by pymta (however you
        can always reject a message using accept_msgdata().