(PHP Contact Page->) Delivery Status Notification (Failure)

[skeet_61]

============
From: postmaster@<hiddentarget>.com
To: wwwrun@linux.<hiddenhost>.com


This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed.

info@greatlakescleaning.com

Final-Recipient: rfc822;info@greatlakescleaning.com
Action: failed
Status: 5.1.1


============

$to = "info@<hiddentarget>.com";
$sub = "Subject.";
$msg = "E-MAIL SENT FROM http://<hidden.com>/contact/\n";
$msg .= "Message:\n\t$comments\n\n";
$mailheaders = "From: Information\n\n";
$mailheaders .= "Reply-To: $email\n\n";
if( mail($to, $sub, $msg, $mailheaders)){
$sent = "true";
} else {
$sent = "false";
}

============

I can send emails from the terminal to any other address fine except the info@<hidden>.com, What is going on?... We dont host the mail for this client, ...

Anyone have a clue?