Moving from hMailServer (Windows) to Postfix (CentOS) server?

Question

postfix

The situation is this: there are 25 mailboxes of the same domain, the hMailServer mail server is on a machine with Windows Server 2012 R2. There is a CentOS virtual machine (Elastix, to be more precise), IP telephony works, the built-in Postfix mail server is not used yet.
How can I use it, abandoning the screw server? Nothing should change - the domain is the same, assigned to our white IP address, all letters must be saved, and this is 70 gigabytes ...
Maybe, in this particular case, saving letters to backup and subsequent restoration will do?

Answer 1

I propose to distill mail using imapsync. At night, start synchronization and change dns records. Then re-synchronization in order to drag what was lost along the way.