ارسال ایمیل با PHP

سلام ...
براي ارسال ايميل يه فرم ساده رو در نظر مي گيريم ...

<form method="POST" action="mail.php">
   <p>Your Email :<input type="text" name="mail_from" size="20"></p>
   <p>Your Mail Subject : <input type="text" name="mail_subject" size="20"></p>
   <p>Your Message : <textarea rows="2" name="mail_body" cols="20"></textarea></p>
   <p><input type="submit" value="Send" name="submit"></p>
</form>

يكي از ساده ترين راههاي ارسال ايميل تو php‏ تابع mail هست ...
و اما اين هم كد :

<?
//Check for send button clicked ...
if(isset($_POST['submit']))
{
$mail_from = isset($_POST['mail_from']) ? htmlspecialchars($_POST['mail_from']) : '';
$mail_subject = isset($_POST['mail_subject']) ? htmlspecialchars($_POST['mail_subject']) : '';
$mail_body = isset($_POST['mail_body']) ? htmlspecialchars($_POST['mail_body']) : '';

//Check Empty fields ...
if($mail_from == '')
{
   die('Please enter Your Email Address. ');
}
if($mail_subject == '')
{
   die('The mail subject is empty ! please enter it. ');
}
if($mail_body == '')
{
   die('The mail body is empty ! please enter it. ');
}

// Mail to (Admin Email )...
$mail_to = "admin@yahoo.com";

//Send mail to admin ...
if(@mail($mail_to,$mail_subject,$mail_body,"From: <$mail_from>\n"))
{
   print("Tank you! Your Message has been sent.");
}
else
{
   print("Error! Sending has stopped .");

}
//End the Sending mail...
}
else
{
?>
<form method="POST" action="mail.php">
   <p>Your Email :<input type="text" name="mail_from" size="20"></p>
   <p>Your Mail Subject : <input type="text" name="mail_subject" size="20"></p>
   <p>Your Message : <textarea rows="2" name="mail_body" cols="20"></textarea></p>
   <p><input type="submit" value="Send" name="submit"></p>
</form>
<?
}
?>

اين كد ها رو در فايلي به نام mail.php ذخیره کنید.
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