if ($mail_alert->add() !== false) {
        die('1');

            $product_name = Product::getProductName($id_customer);
            $shop_email = 'my-email-for-test@email.com';
            $shop_name = Configuration::get('PS_SHOP_NAME');
            $dir_mail = dirname(__FILE__).'/../../mails/';
            $template_vars = array(
                '{customer_email}' => $customer_email,
                '{product_name}' => $product_name
            );

            Mail::Send(
                $id_lang,
                'new_oos',
                Mail::l('New request of product', $id_lang),
                $template_vars,
                (string)$shop_email,
                null,
                (string)$shop_email,
                (string)Configuration::get('PS_SHOP_NAME', null, null, $id_shop),
                null,
                null,
                $dir_mail,
                false,
                $id_shop
            );

    } else {
        die('0');
    }
}

Server: smtp.gmail.com (if you uses gmail)

Username: your gmail id

Password: your gmail password

Encryption: SSL

Port: 465