Multiple domains?

Hello list,

we are reflecting on offering 'MSExchange Services' to our customers for their domain hostings on our servers. We are targeting small offices/companies with 5 to 20 users. Finding groupware products, based on Linux of course, isn't that hard however, when it comes to multi domain functionality, none of them is left... And, synchronization with Outlook is a must as well.

We cannot set up a server for every small domain to serve. We would need to find a way to get multi domains working. They should all be working within their domain itself. Therefore I am thinking of different possibilities to achieve this:

1. Setting up different groups for each domain on the same groupware installation. However, group members must be invisible to members in other groups.

2. The software is already capable of handling multiple domains.

3. It is possible to set up different instances of the groupware software, for example by using different tables or multiple databases on the same server, possibly listening on different ports.

Since I do not know the details of the opengroupware software I would like to ask and hear from you users any input and comments on the suggestions I made above. Maybe one or the other may work out, depening also on the configurability of the software itself.

Thanks, Dave