We are currently running a postfix mail server and are considering upgrading to Zimbra. The big hiccup is migration. I've seen several suggestions to use imapsync as a migration tool from IMAP to IMAP going from a standalone postfix to Zimbra. The deal breaker for this is having to know all users passwords.

Since Zimbra is using postfix on the back end, is it possible just to copy the data stores from my standalone postfix installation to the zimbra postfix installation? If Zimbra is using a stock postfix, isn't this the equivalent of restoring from a backup? Perhaps a few mailbox reconstructs might be necessary, but, in principle, shouldn't this work?