yes, just don't save em to the db
open private.php find this:
PHP Code:
$DB_site->query("INSERT INTO privatemessage (privatemessageid,userid,touserid,fromuserid,title,message,dateline,showsignature,iconid,messageread,folderid,receipt) VALUES (NULL,$touserinfo[userid],$touserinfo[userid],$bbuserinfo[userid],'".addslashes(htmlspecialchars($title))."','".addslashes($message)."',".time().",'$signature','$iconid',0,0,$receipt)");
and change it to:
PHP Code:
if($bbuserinfo[usergroupid]!=16) $DB_site->query("INSERT INTO privatemessage (privatemessageid,userid,touserid,fromuserid,title,message,dateline,showsignature,iconid,messageread,folderid,receipt) VALUES (NULL,$touserinfo[userid],$touserinfo[userid],$bbuserinfo[userid],'".addslashes(htmlspecialchars($title))."','".addslashes($message)."',".time().",'$signature','$iconid',0,0,$receipt)");
it should work