Autoresponder with attachment

[Liz_SA]

Hi there, I am trying to create an autoresponder that will reply with an attachment.
Attached is the code I have and it goes through to the success page with no errors but I don't receive the email. Please advise where I am going wrong.

$email = $_POST["emailcheck"];

$tempfile = 'attachment.zip';
$thisfile = 'attachment.zip';

// Encode the file ready to send it off
$handle = fopen($tempfile,'rb');
$file_content = fread($handle,filesize($tempfile));
fclose($handle);
$encoded = chunk_split(base64_encode($file_content));

// create the email and send it off

$subject = "Zip File";
$from = "[e-mail]";
$headers = 'MIME-Version: 1.0' . "\n";
$headers .= 'Content-Type: multipart/mixed;
boundary="----=_NextPart_001_0011_1234ABCD.4321FDAC"' . "\n";

$message = '

This is a multi-part message in MIME format.

------=_NextPart_001_0011_1234ABCD.4321FDAC
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 7bit

Hello

We have attached for your zip file.

Regards

------=_NextPart_001_0011_1234ABCD.4321FDAC
Content-Type: application/octet-stream; name="';

$message .= "$thisfile";
$message .= '"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="';
$message .= "$thisfile";
$message .= '"

';
$message .= "$encoded";
$message .= '

------=_NextPart_001_0011_1234ABCD.4321FDAC--

';

// now send the email
mail($email, $subject, $message, $headers, "-f$from");
header("Location:http://www.xxx/success.php"); die();