public function getMissingContacts($websiteId, $pageSize = 100)
    {
        $collection = $this->addFieldToFilter('contact_id', ['null' => true])
            ->addFieldToFilter('suppressed', ['null' => true])
            ->addFieldToFilter('website_id', $websiteId);

        $collection->getSelect()->limit($pageSize);

        return $collection->load();
    }