Migration from kerio to Exchange. Need advice on what to do?

Question

Microsoft Exchange

Greetings. There is a task to migrate from one mail carrier to another. Kerio stupidly cannot cope with a 400GB database, it happens. So. I thought about three options for myself.
1.Exchange becomes a forwarding server, later the old one is turned off and the new one becomes the main
one 2.Exchange is configured as a second working server with a new name with a direct zone, etc. Here the question arises, how to make two mailers on one external ip.25 port is busy, use another port?
3. Get an external ip and use it calmly.
If anyone solved such a problem, tell me how it is more convenient? You can do it on time even on weekends so as not to distract anyone, as I understand the forwarding server is organized for the uninterrupted operation of mail

Answer 1

I am for the first option:
1. Raise Exchange, make your zone on it Internal Relay + Send Connector from Smart Host to your Kerio.
2. On the ekschendzha, configure the Send Connector to the outside world
3. On Kerio, send via the ekschendzh.
further it will be difficult for me to describe the algorithm, because I'm not familiar with Kerio
4. Create a new temporary accepted domain on the exchange, like tmp.mydomain.ru
5. Configure the correct routing to this domain on Kerio
6. Make a test user, a pilot one on kerio, a mailbox for a couple of megabytes, then export to pst, create a mailbox on ekscha, assign him the addresses [email protected], and [email protected], everything from the moment the mail was created to [email protected] mailbox will remain on the exchange. On kering, the mailbox is deleted or unconditional forwarding is set to [email protected]
After a successful pilot, prepare batches and migrate all users.
PS
Step 6 may have variations. For example, vice versa, on Kerio, you create additional @tmp.mydomain.ru mailboxes for everyone, on Exchange, start mailboxes for everyone, with unconditional redirection of all mailboxes incoming to Kerio. Thus, slowly synchronize kerio in the exchange, well, that is. different approaches can be considered. But usually they take money for it -)

Answer 2

Thanks for the answer and for the info. Well, let's just say, I already installed Exchange.
Is it even possible to have two mail servers on a local network? Which will have two mail domains?