roundcubemail-plugins-kolab/plugins/owncloud/config.inc.php.dist

<?php

// ownCloud URL
$rcmail_config['owncloud_url'] = 'https://owncloud.webmail.tld';

// authentication exchange secret
// has to be the same as the value for 'kolabsecret' in owncloud config
$rcmail_config['owncloud_secret'] = '<shared-secret-string>';