电子邮件脚本报告成功，但电子邮件不会出现在我的收件箱中

我创建了一个链接到PHP页面的表单，如下所示：

<form method="get" action="contact.php">
<p>Nome:</p> <input type="text" name="name" class="name" /><br>
<p>E-mail :</p> <input type="text" name="mail" class="mail" /><br>
<p>Website:</p> <input type="text" name="website" class="website" /><br>
Mensagem: <textarea name="message" class="message" rows="2" cols="20"></textarea>        
<input type="submit" value="Enviar" class="submit" />
</form>

PHP页面：

<?php 
$field_name = $_GET['name'];
$field_email = $_GET['mail'];
$field_website = $_GET['website'];
$field_message = $_GET['message'];
$mail_to = '__munged__@gmail.com';
$subject = 'Message from a site visitor ' . $field_name;
$body_message = 'From: '.$field_name."'n";
$body_message .= 'E-mail: '.$field_email."'n";
$body_message .= 'Message: '.$field_message;
$headers = "From: $field_email'r'n";
$headers .= "Reply-To: $field_email'r'n";
$mail_status = mail($mail_to, $subject, $body_message, $headers);
if ($mail_status) { ?>
<script language="javascript" type="text/javascript">
    alert('Thank you for the message. We will contact you shortly.');
    window.location = 'index.html';
</script>
<?php
}
else { ?>
<script language="javascript" type="text/javascript">
    // Print a message
    alert('Message failed. Please, send an email to __munged__@template-help.com');
window.location = 'index.html';
</script>
<?php
}?>

我似乎想不通这个问题。提前谢谢。