def __init__(self, service, portal = None):
        """
        @type service: L{MailService}
        @param service: An email service.

        @type portal: L{Portal <twisted.cred.portal.Portal>} or
            L{None}
        @param portal: A portal to use for authentication.
        """
        smtp.SMTPFactory.__init__(self)
        self.service = service
        self.portal = portal

        @type service: L{MailService}
        @param service: An email service.

        @type portal: L{Portal <twisted.cred.portal.Portal>} or
            L{None}
        @param portal: A portal to use for authentication.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/protocols.py