public function getBccEmailOfMessage($messageId)
    {
        $message = $this->client->get("inboxes/{$this->config['inbox_id']}/messages/$messageId/body.eml")->getBody();

        if ($message instanceof Stream) {
            $message = $message->getContents();
        }
        $matches = [];
        preg_match('/Bcc:\s[\w.-]+@[\w.-]+\.[a-z]{2,6}/', $message, $matches);

        $bcc = substr(array_shift($matches), 5);

        return $bcc;
    }