Cannot send email in localhost

why i can't send email in localhost but when i try in hosting it can send email this my code **

define('ROOT', 'localhost/OMG1/');
$kode = md5(uniqid(rand()));
$to = $_GET['f11'];
        $headers = "From: rizka.nugroho@omg-indonesia.com\r\n";
        $headers .= "Reply-to: $to\r\n";
        $pesan    = "Klik link berikut untuk verifikasi dan mengaktifkan akun : ";
        $pesan    .= ROOT."active.php?email=".$_GET['f11']."&kode=$kode&username=".$_GET['f5'];var_dump($pesan);
$a = @mail($to, "Aktivasi Akun Anda", $pesan, $headers);var_dump($a); 
if($a)
        {
            echo "Email send";
        }
        else
        {
            echo "failed to send mail";
        }

** please help solved my problem