Zimbra with existing mail/SQL server

[fogogg]

Thanks for taking the time to read this.

I am looking at bringing up a Zimbra server on our network to support ~100 users. I have an existing postfix/courier mail server which is also running a MySQL server dedicated to the email system. It is being accessed by Thunderbird inside the the network and via a separate machine running E-Groupware which is accessible both inside and outside the network.

I would like to make the change as smoothly as possible. Can I replace the E-Groupware installation with Zimbra and have it remotely access the mail server to retrieve users mail? Additionally, does Zimbra use MySQL for functions such as calendaring and can I also access that from a remote installation of Zimbra?

I apologize if this has been covered thoroughly already. I searched and found nothing similar to my request.