code: public function export()
      {
          // moved initialization of subject here because of the following issue
          // https://github.com/yiisoft/yii2/issues/1446
          if (empty($this->message['subject'])) {
              $this->message['subject'] = 'Application Log';
          }
          $messages = array_map([$this, 'formatMessage'], $this->messages);
          $body = wordwrap(implode("\n", $messages), 70);
          $message = $this->composeMessage($body);
          if (!$message->send($this->mailer)) {
              throw new LogRuntimeException('Unable to export log through email!');
          }
      }
docs: Sends log messages to specified email addresses.
  Starting from version 2.0.14, this method throws LogRuntimeException in case the log can not be exported.
  @throws LogRuntimeException