def __getstate__(self):
        """
        Helper for pickle.

        protocol isn't picklabe, but we want User to be, so skip it in
        the pickle.
        """
        return { 'dest' : self.dest,
                 'helo' : self.helo,
                 'protocol' : None,
                 'orig' : self.orig }

        Helper for pickle.

        protocol isn't picklabe, but we want User to be, so skip it in
        the pickle.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/smtp.py