In a subdomain network, what .htaccess settings can I use to have WP ignore requests to one subdomain?

I found this article: http://codex.wordpress.org/Configuring_Wildcard_Subdomains_for_multi_site_under_Plesk_Control_Panel

I had used it originally when setting up the wildcard subdomains on my Plesk server. At first I didn’t need to worry about the webmail section, but now I do, and here’s what I did:

$ cd /etc/apache2/conf.d
$ mv zzz_horde_vhost.conf zz001_horde_vhost.conf
$ /etc/init.d/apache2 restart

This way, the Horde config will be loaded before the wildcard subdomains.