def sendmail_sync(
        self,
        sender: str,
        recipients: RecipientsType,
        message: Union[str, bytes],
        mail_options: Iterable[str] = None,
        rcpt_options: Iterable[str] = None,
        timeout: DefaultNumType = _default,
    ) -> SendmailResponseType:
        """
        Synchronous version of :meth:`.sendmail`. This method starts
        the event loop to connect, send the message, and disconnect.
        """
        return self._run_sync(
            self.sendmail,
            sender,
            recipients,
            message,
            mail_options=mail_options,
            rcpt_options=rcpt_options,
            timeout=timeout,
        )