Is it posseble to give some "default" Apache Directives? What i seek is to do reverse proxy to the webmail at port 81 so all customers get customer.com/webmail, is there anything like it? or any bether sollutions..
You can either use the "Apache Directives" field (which wouldn't be automatic), or you have a look at the function make_vhost() in /root/ispconfig/scripts/lib/config.lib.php.