return-receipt-to: in mail()

[Anon]

Hi,
I've been fooling around with trying to get

$mailheaders .= "Return-Receipt-To: " . $returnreceipt . "\r\n";

to work in the mail() function.

Everything else works fine, but a return-receipt is never sent. Is this dependent on the mail server?
Or does anyone have any hints for me?

in context:

$email = "[e-mail]";
$fromemail = "[e-mail]";
$returnreceipt = "[e-mail]";

$mailheaders = "From:" . trim($fromemail) . "\r\n";
$mailheaders .= "Return-Receipt-To:" . trim($returnreceipt) . "\r\n";
mail($email, $subject, $msg, $mailheaders);

thanks,
Ben