Transferring mail (postfix+dovecot) to another server?

Question

Mail server

Good day to all!
how painlessly (without stopping the work of users) to transfer the mail server to another dedicated server. I thought about Fetchmail (for new letters, specify the ip of the new server with a directory for storage, then when I finish the configs, I will already transfer all the mail)
By what principle to store data, 140-150 mailboxes maximum, I think to do without MySQL.

Answer 1

Two ways to migrate postfix+dovecot - serverfault.com/questions/611143/how-to-migrate-a-... In my opinion, it's convenient to manage Postfix through PostfixAdmin and store mailboxes as maildirs.