Index: modules/user/user.module
===================================================================
--- modules/user/user.module	(revision 25910)
+++ modules/user/user.module	(working copy)
@@ -3430,7 +3430,7 @@
     $params['account'] = $account;
     $language = $language ? $language : user_preferred_language($account);
     $mail = drupal_mail('user', $op, $account->mail, $language, $params);
-    if ($op == 'register_pending_approval') {
+    if ($op == 'register_pending_approval' && variable_get('user_mail_register_pending_approval_admin_notify', TRUE)) {
       // If a user registered requiring admin approval, notify the admin, too.
       // We use the site default language for this.
       drupal_mail('user', 'register_pending_approval_admin', variable_get('site_mail', ini_get('sendmail_from')), language_default(), $params);