reverted:
--- b/core/modules/update/update.fetch.inc
+++ a/core/modules/update/update.fetch.inc
@@ -38,7 +38,7 @@
         else {
           $target_langcode = $default_langcode;
         }
+        $message = \Drupal::service('plugin.manager.mail')->mail('update', 'status_notify', $target, $target_langcode, $params);
-        $message = \Drupal::service('plugin.manager.mail')->mail('update', 'status_notify', $target, $target_langcode, $params, NULL, TRUE);
         // Track when the last mail was successfully sent to avoid sending
         // too many emails.
         if ($message['result']) {