Plesk alias on a subdomain

If you need another domain name pointing to an existing subdomain, create a file in the subdomains conf directly like this:

vi /var/www/vhost/yoursite.com/subdomains/foo/conf/vhost.conf

contents:

ServerAlias "newaliasname.com"
ServerAlias "www.newaliasname.com"

then rebuild apache config like:

/opt/psa/admin/sbin/httpdmng --reconfigure-all