falha no função mail()

Srs. Ajuda pf.

Já quebrei a cabeça mas não resolvi...

Script

******************

	<?php

	$SenderAddress = "test@test.com";

	define('OCU_RELEASE', '1.1');

	define('OCU_ERR', !empty($_GET['err']));

	if (OCU_ERR) {

	    error_reporting(E_ALL);

	    ini_set('display_errors', 'On');

	}

	else {

	    error_reporting(0);

	}

	if (basename(__FILE__) == '1cu.php') {

	    die('For your safety: you should really change the name of this file');

	}

	if (!empty($_GET['test'])) {

	    die("OK: ".OCU_RELEASE);

	}

	if (empty($_GET['l']) && empty($_GET['e'])) {

	    die("OK");

	}

	$l = isset($_GET['l']) ? $_GET['l'] : '';

	$e = isset($_GET['e']) ? $_GET['e'] : '';

	$m = isset($_GET['m']) ? $_GET['m'] : '';

	$l = OCU_Unencode($l);

	$e = OCU_Unencode($e);

	$to      = $l;

	$subject = "Unsubscribe";

	$message = "Unsubscribe $e";

	$from     = $e;

	if ($SenderAddress != 'test'.'@'.'test'.'.com') {

	    $from = $SenderAddress;

	}

	switch ($mode) {

	    case "1":

	        $headers = "X-UserMail: $e";

	        break;

	    case "2":

	        $headers = "From: $from";

	        break;

	    default:

	        $headers = "From: $from" . "\r\n" . "X-UserMail: $e";

	}

	if (mail($to, $subject, $message, $headers)) {

	    Header("Location: removal.htm");

	} else {

	    die("There was an error processing your request; please manually send an email to $l with Unsubscribe as its subject");

	}

	exit;

	function OCU_Unencode($data) {

	    return base64_decode(strtr($data, '-_', '+/'));

	}

	?>

	***************************

	Não envia de maneira nenhuma.

	Alguém pode me ajudar?