[horde] configurating more than one domain

[xare]

I provide service to more than one user and more than one domain.

How can I do to direct userA from domainA and userB from domainB to their
inboxes?

I plan to open both subdomains mail.domainA.tld and mail.domainB.tld and
userA should go to the first and userB should go to the second one, and then
login.

1. I have created mail.domainA.tld pointing to /var/www/html/horde/imp in my
system but the loging screen at least would not take the stylesheet
correctly.
2. Then I pointed in apache to /var/www/html/horde. The result is a very
long time to wait and resulting in a blank screen.

I am using the latest horde distribution.

Bye and thanks