Simple script, that shows / extract all email addresses of customers, who made orders in the Magento shop

gistfile1.php

<?php
/**
 * @author Tsvetan Stoychev <ceckoslab@gmail.com>
 * @license http://opensource.org/licenses/osl-3.0.php Open Software License (OSL 3.0)
 */
ini_set('max_execution_time', 0);

define('MAGENTO_ROOT', getcwd());
$mageFilename = MAGENTO_ROOT . '/app/Mage.php';
require_once $mageFilename;

ini_set('display_errors', 1);

umask(0);
Mage::app();


$ordersCollection = Mage::getModel('sales/order')->getCollection()
                                                ->addFieldToSelect('customer_email');

$ordersCollection->getSelect()
                        ->columns(array('orders_count' => 'COUNT(customer_email)'))
                        ->group('customer_email');


echo '<pre>';
foreach($ordersCollection as $order) {
    echo $order->getData('customer_email') . '<br />';
}
echo '</pre>';