We're currently evaluating Zimbra as one of a number of possible solutions, where we will need to provide two distinctly different classes of service to users. One CoS will have full Outlook integration, the second will have a standard web-based interface for the collaboration suite.

Now, I know Zimbra can do both of these, and one solution would be to have two Zimbra servers (one O/S and the other Network)... HOWEVER... we have to be able to share calendars, etc, between the two. There are going to be a number of different domains hosted in the solution, and any particular domain will contain a mix of Outlook and Web based users.

Is this type of mixed-mode installation possible with Zimbra?

(The reason we want to keep with the Open Source version for Web users is purely to do with price. We can't justify paying $28pa for every user when less than 5% of them are going to use the enhanced functionality. Unfortunately those 5% are influential enough users that if we can't meet their needs then they will veto the solution.)