def reset_state(self):
        """
        Resets some attributes to their default values.

        This is especially useful when initializing a newly created
        :class:`SMTP` instance and when closing an existing SMTP session.

        It allows us to use the same SMTP instance and connect several times.
        """
        self.last_helo_response = (None, None)
        self.last_ehlo_response = (None, None)

        self.supports_esmtp = False
        self.esmtp_extensions = {}

        self.auth_mechanisms = []

        self.ssl_context = False

        self.reader = None
        self.writer = None
        self.transport = None