def sentMail(self, code, resp, numOk, addresses, log):
        """Since we only use one recipient per envelope, this
        will be called with 0 or 1 addresses. We probably want
        to do something with the error message if we failed.
        """
        if code in smtp.SUCCESS:
            # At least one, i.e. all, recipients successfully delivered
            os.remove(self.names[0] + '-D')
            os.remove(self.names[0] + '-H')
        del self.messages[0]
        del self.names[0]
Since we only use one recipient per envelope, this
        will be called with 0 or 1 addresses. We probably want
        to do something with the error message if we failed.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/relay.py