private function buildDestination($emails) 
    {
        $ret = ['ToAddresses' => isset($emails['to']) ? $emails['to'] : array_values($emails)];
        if (isset($emails['cc']) && $emails['cc'])
            $ret['CcAddresses'] = $emails['cc'];
        if (isset($emails['bcc']) && $emails['cc'])
            $ret['BccAddresses'] = $emails['bcc'];
        return $ret;
    }