public function transport_auth($driver)
    {
        switch ($driver) {
        case 'foo':
            // Example #1: Use full Horde username for password.
            // This is generally needed for sieve servers.
            $full_user = $GLOBALS['registry']->getAuth(null);
            return array(
                'euser' => $full_user,
                'username' => $full_user
            );
//
//            // Example #2: Use IMP password/username.
//            $ob = $GLOBALS['registry']->call('mail/imapOb');
//            return array(
//                'password' => $ob->getParam('password'),
//                'username' => $ob->getParam('username')
//            );
        }
//
//        // DEFAULT: Use hordeauth (identical to not defining hook at all).
//        return true;
    }