Try:
$id =101;
$comments = EmailArchive::model()->findAll(
array("condition"=>"email_id = $id","order"=>"id"));
OR
$id =101;
$criteria = new CDbCriteria();
$criteria->addCondition("email_id=:email_id");
$criteria->params = array(':email_id' => $id);
$comments = EmailArchive::model()->findAll($criteria);
OR
$Criteria = new CDbCriteria();
$Criteria->condition = "email_id = $id";
$Products = Product::model()->findAll($Criteria);