I have installed the Horde Groupware Webmail Edition. I have created a subdomain for it. I am running it on my ISPC3 server. It is dedicated for my own domain. It seems working fine for me. I have not tried it while setting up for other domain. You might try it yourself.
I have posted a reply about this here
. I used a how-to I found. It helped me to install it in an easy way.