There was a problem checking available updates [1] for Drupal.
See the available updates page for more information:
http://www.rentin24.com/drupal1/?q=admin/reports/updates
Your site is currently configured to send these emails when any updates are
available. To get notified only for security updates,
http://www.rentin24.com/drupal1/?q=admin/reports/updates/settings.
[1] http://www.rentin24.com/drupal1/?q=admin/reports/updates