How to replace the mail server correctly?

Question

postfix

Colleagues.
The mail server has been replaced. We are currently using Postfix. We are planning to deploy Exchange A
lot of work emerges from here. I understand that to transfer boxes and users - that still a problem. But the most annoying thing is how to do it without interfering with the circulation of mail. In one day, you still can’t drag everyone, but you need mail to continue to go.
What will be the options? Raise another domain? Set up some kind of connection between servers? What do you advise? Have you had a similar experience?

Answer 1

1) Specify Postfix as SMTP relay in Exchange.
2) Hide Cyrus behind Nginx IMAP proxy.
By default, Nginx sends everyone to Cyrus, from an explicit list - to Exchange.
A good setup example: www.alsigned.ru/?p=3189
3) Transfer all mailboxes one by one from Cyrus to Exchange using imapsync.
4) After copying the next mailbox, add the email to the list for Nginx and to /etc/postfix/transport:
[email protected] :[ip-address-exchange]
Then postmap transport and postfix reload.
Those. postfix will send received emails not to Cyrus, but to Exchange.
More or less like this.

Answer 2

in any case, you will need a constantly available backend server, where there will be all user data and a second mx-record (10 and 20, for example), so that uptime
with exchange does not work, unfortunately. experience was with communicate - there the data was stored in an open form. When switching to new hardware, I transferred data to the backend server and raised the frontend for clients. BUT this is a transition within one product. Look at the functionality, it may work out, although you know the Microsoft principles - I doubt (