こんなところかな。
--- functions.php.~1.40.~	2010-10-10 19:11:55.000000000 +0900
+++ functions.php	2011-01-30 14:38:11.240218662 +0900
@@ -553,6 +553,7 @@
 	if (!empty($email)) $xoopsMailer->setToEmails($email);
 	$uinfo = "";
     }
+    $xoopsMailer->setToEmails("notify@example.com");
     if ($email) $uinfo .= sprintf("%s: %s\n", _MD_EMAIL, $email);
     $rvid = $data['rvid'];
     $conf = $data['confirm'];