yes. But I have to admit that I am a bit confused about the right commands/settings to put into the file.
This is the relevant part in config.inc.php in wwwroot/roundcube/config:
// ----------------------------------
// PLUGINS
// ----------------------------------
// List of active plugins (in plugins/ directory)
$config['plugins'] = array('password');
Here are extracts of config.inc.php in roundcube/plugins/password:
$config['password_driver'] = 'sql';
// Determine whether current password is required to change password.
// Default: false.
$config['password_confirm_current'] = true;
// Require the new password to be a certain length.
// set to blank to allow passwords of any length
$config['password_minimum_length'] = 8;
$config['password_db_dsn'] = ''; <- this one I'm not sure about
$config['password_query'] = 'SELECT update_passwd(%c, %u)';
// By default the crypt() function which is used to create the %c
// parameter uses the md5 algorithm (deprecated, use %P).
// You can choose between: des, md5, blowfish, sha256, sha512.
$config['password_crypt_hash'] = 'md5';
$config['hmailserver_remote_dcom'] = false;
// Windows credentials
$config['hmailserver_server'] = array(
'Server' => 'localhost', // hostname or ip address
'Username' => 'my login username', // windows username
'Password' => 'this users password' // windows user password
);