Issue #2893655 by hanoii: Swiftmailer stopped working

    ];

    $message['body'] = trim((string) \Drupal::service('renderer')->renderPlain($build));

    if ($this->configuration['html']) {

      switch ($this->getMailSystemSender()) {

        case 'swiftmailer':

          // SwiftMailer requires that the body be valid Markup.

          $message['body'] = Markup::create($message['body']);

          break;

      }

    }

    // Send message.

    $this->mailManager->mail('webform', 'email_' . $this->getHandlerId(), $to, $current_langcode, $message, $from);