def do_RSET(self):
        """
        Handle a RSET command.

        Unmark any messages that have been flagged for deletion.
        """
        try:
            self.mbox.undeleteMessages()
        except:
            log.err()
            self.failResponse()
        else:
            self._highest = 0
            self.successResponse()

        Handle a RSET command.

        Unmark any messages that have been flagged for deletion.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/pop3.py