cmc-sales/controllers/email_attachments_controller.php

<?php
class EmailAttachmentsController extends AppController {

    var $name = 'EmailAttachments';
    var $helpers = array('Html', 'Form');


    function download($id) {
        Configure::write('debug', 0);
        $file = $this->EmailAttachment->findById($id);
        header('Content-type: ' . $file['EmailAttachment']['type']);
        header('Content-length: ' . $file['EmailAttachment']['size']);
        header('Content-Disposition: attachment; filename='.basename($file['EmailAttachment']['name']));
        header('Content-Transfer-Encoding: binary');
        header('Expires: 0');
        header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
        ob_clean();
        flush();
        readfile($file['EmailAttachment']['filename']);
        //  echo $file['EmailAttachment']['filename']
        exit();
    }

}