[horde] Three separate userbases with automatic IMAP login

[Jarkko Ranta]

Hello, good people.

I have a problem which I could possibly solve with some serious 
Trial&Error, but since the different approaches in my problem are so 
numerous, I thought I'd rather ask your help.

I would like to install three Horde Groupware Webmail suites to three 
different groups of people. I wan't the users of each installation to be 
able to see each other (and each others calendars etc.), mut not be aware 
of the users of the other two installations.

What kind of installation do you recommend?

If I create mail addresses for all the groups, can I use IMP 
authentication for them and STILL be able to separate the users into 
different 'installations'? I'd just like the users to autologin to their 
mailboxes at the Horde login, so that's why I'd like to use IMP 
authentication, or is there another way?

So, I guess here it is in a nutshell:
- 3 Horde Groupware Webmail Edition userbases. (should I use 
same database or create each it's own, effectively being 3 totally 
separate Groupware installations?)
- Each installation has a different userbase, in which the users are able 
to see other users in the same 'installation', but are unaware of other 
userbases' users
- Users should login into their IMAP boxes directly when they log on to 
Horde, without separate mailbox login.

Is there a simple answer for this? :)

-jarkko