I am very interested in deploying Zimbra at my enterprise. Our trusty Postfix/Dovecot setup has been working just fine, but we need the ability to collaborate/share calendars, and we do not want to invest in Exchange when Zimbra looks like it will do what we need.

Here is the scenario: I want to deploy Zimbra community edition, and I do not want to migrate mail boxes away from my current Postfix/Dovecot server. Is it possible to use Zimbra CS while keeping my existing mailboxes on the existing server and still use shared calendars, etc.

Also, can I use Outlook as my client, and share calendars, without needing an Outlook connector? I want everyone to see everybody's calendars, etc.