Solution 1:
Am sure on the postfix system you are running some sort of imap server, you can use imapsync to migrate the mail across to the exchange server while retaining the message flags.
Postfix to Exchange Migrate Mailboxes
Solution 1:
Am sure on the postfix system you are running some sort of imap server, you can use imapsync to migrate the mail across to the exchange server while retaining the message flags.