def init_app(cls, app):
        Config.init_app(app)

        # email errors to the administrators
        import logging
        from logging.handlers import SMTPHandler
        credentials = None
        secure = None
        if getattr(cls, 'MAIL_USERNAME', None) is not None:
            credentials = (cls.MAIL_USERNAME, cls.MAIL_PASSWORD)
            if getattr(cls, 'MAIL_USE_TLS', None):
                secure = ()
        mail_handler = SMTPHandler(
            mailhost=(cls.MAIL_SERVER, cls.MAIL_PORT),
            fromaddr=cls.FLASKY_MAIL_SENDER,
            toaddrs=[cls.FLASKY_ADMIN],
            subject=cls.FLASKY_MAIL_SUBJECT_PREFIX + ' Application Error',
            credentials=credentials,
            secure=secure)
        mail_handler.setLevel(logging.ERROR)
        app.logger.addHandler(mail_handler)