error occurred in email script in php

Question

email script -

$subject = "[New Order] " . $_SESSION['orderId'];
$email   = $shopConfig['email'];
$message = "You have a new order. Check the order detail here \n http://" .     $_SERVER['HTTP_HOST'] . WEB_ROOT . 'admin/order/index.php?view=detail&oid=' . $_SESSION['orderId'] ;
mail($email, $subject, $message, "From: $email\r\nReturn-path: $email"); //line 20th

Warning: mail() [function.mail]: SMTP server response: 553 sorry, relaying denied from your location [173.201.196.177] (#5.7.1) in D:\Hosting\6448289\html\products\success.php on line 20

why is it throwing such error?

Answer 1

This is an authorisation error, not a problem with PHP.

See http://ask-leo.com/why_does_email_bounce.html for more details on this specific issue.