altFilter example

$body = $template->fetch('newsletter/index/' . $mailing['template'], $template);
        } else {
            $body = $template->fetch('newsletter/alt/' . $mailing['template'], $template);
        }

        if (empty($mailing['plaintext'])) {
            if (!$this->Request()->getParam('id')) {
                $body = $this->trackFilter($body, $mailing['id']);
            }
        } else {
            $this->Response()->headers->set('content-type', 'text/plain');
            $body = $this->altFilter($body);
        }

        echo $body;
    }

    /** * Mail action method * * Sends one or more newsletter emails. */
    public function mailAction()
    {