メールフォームの値を任意の値に書き換えたい

if (!empty($mailFields)) {

	foreach ($mailFields as $key => $record) {
		if($record['MailField']['field_name'] == 'name'){
			$record['MailField']['default_value'] = 'おーおー';
		}

class myPluginControllerEventListener extends BcControllerEventListener {

	public $events = array(
		'Mail.Mail.beforeRender'
		);
	
	public function mailMailBeforeRender(CakeEvent $event) {
		if (BcUtil::isAdminSystem()) {
			return;
		}
        $Controller = $event->subject();
        foreach($Controller->viewVars['mailFields'] as $key => $field){
	        if($field['MailField']['field_name'] == 'name'){
		        $Controller->viewVars['mailFields'][$key]['MailField']['default_value'] = 'おーおー';
	        }
        }
	}
}