This is your safest way to do it:
$id =101;
//$user_id=25;
$criteria=new CDbCriteria;
$criteria->condition="email_id < :email_id";
//$criteria->addCondition("user_id=:user_id");
$criteria->params=array(
':email_id' => $id,
//':user_id' => $user_id,
);
$comments=EmailArchive::model()->findAll($criteria);
Note that if you comment out the commented lines you get a way to add more filtering to your search.
After this it is recommend to check if there is any data returned like:
if (isset($comments)) { // We found some comments, we can sleep well tonight
// do comments process or whatever
}