Gradual migration from postfix to Exchange?

Question

postfix

Good afternoon.
There is a company.local domain with 50+ users and a Postfix server (company.com) connected to the domain using LDAP.
Task: smoothly transfer all users from postfix to Exchange. That is, in fact, users will have to be able to receive mail from both postfix and exchange for some time (which will be spent on the transition).
As I see it for myself:
1. We put the ex (I don’t see any problems for myself here)
2. We set up the forwarding of incoming mail from the postfix server to the ex (there are problems here, because very, very few have encountered setting up * nix servers.)
3. Smoothly upload (via IMAP) mail from email clients (mostly Thunderbird) to Exchange, install Outlook, configure it to work with Exchange. And so 50+ times, until all users are on Exchang'e (there are no questions here either, mechanical routine work)
4. Remove message forwarding from the old server to the new one, forward ports from the Linux server to the server with Exchange(?)
stones:
1. Now there is a mailbox on postfix, to which all incoming and outgoing mail is sent automatically. Used as a backup. How it is implemented is not clear. It was long before me, the contacts of the old admin were lost
2. The name of the Windows domain is company.local , the name of the domain to which mail will be sent (and is coming now) is company.com
Actually, I need help on steps 2 and 4, maybe a little on the first one (the part with the initial Exchange setup). I honestly used Google, just in terms of steps 2 and 4 I did not find anything sensible and understandable.
Thank you in advance.

Answer 1

I would like to scold a little those who made such a decision, hmm.
Although I really hope that there are some real prerequisites for it.
For the second and even the fourth - for example, like this: www.linuxmail.info/backup-mail-postfix/
That is, enable sending copies to your mail server. And by the way, the current backup is made in about the same way.
Well, the fourth step can be solved in different ways, for example, with the same postfix (read man transport postfix), or with any proxying tools, such as iptables, and, for example, nginx.

Answer 2

1. Install Exchange, set up send/receive connectors, set accepted domains, set recipient policy
2. That's right, we relay the entire company.com -> Exchange IP zone (don't forget to open smtp
) to. users' mail will remain in their old zanderbird - they will also be able to receive it through something you have (Dovecot?
) , and after checking, relay mail to Exchange
5. Take the third step, no longer in a hurry - when the mail goes and leaves Exchange.