Sevgili ustalar Uğrşamama rağmen aşağıdaki hatayı bulamıyorum mail göndermiyo yardım ederseniz sevinirim

Site: Form

<?php 

if (!isset($_POST['submit'])) 
{ 
    echo ' 
    <form action="" method="post"> 
        <input type="text" name="eposta" value="" /> 
         <input type="text" name="telefon" value="" /> 
        <input type="submit" name="submit" value="Gönder" /> 
    </form>'; 
} 
else 
{ 

$g_mail = "admin@giriniz.net";
$baslik = "Deneme Maili";   // Bu kısımda türkçe karakter kullanmamaya özen gösterin
$mesaj = htmlspecialchars($_POST['eposta']);
$telefon = htmlspecialchars($_POST['telefon']);
$header = "From: $g_isim <".$g_mail.">\n"; 
$header .= "Reply-To: $g_isim <".$g_mail.">\n";
$header .= "Return-Path: $g_isim <".$g_mail.">\n";  
$header .= "Delivered-to:  $g_isim <".$g_mail.">\n";
$header .= "Date: ".date(r)."\n";
$header .= "Content-Type: text/html; charset=iso-8859-9\n";   
$header .= "MIME-Version: 1.0\n";
$header .= "Importance: Normal\n";
$header .= "X-Sender: $g_isim <".$g_mail.">\n";   
$header .= "X-Priority: 3\n";   
$header .= "X-MSMail-Priority: Normal\n";
$header .= "X-Mailer: Microsoft Office Outlook, Build 11.0.5510\n";
//$header .= "Disposition-Notification-To: $g_isim <".$g_mail.">\n";
$header .= "X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869\n";

           $gonder = mail('b6762020@hotmail.com', 'E-posta Adresi', $baslik, $mesaj, $telefon, $header); 
     
    echo $gonder ? 'Gönderildi' : 'Yollanmadı!'; 
} 

?>