How to transfer mail with saving all letters?

Question

Mail server

Good time of the day. The company decided to change mail servers. But there was a problem: it is necessary to save all letters in boxes. I understand that this can be done by a banal forwarding, but the functions of the mail provider (hosting) are limited and you will have to send one letter at a time. Is it possible to do this in some other way? Is it possible to take a mail client (The Bat, Thunderbird) to save letters locally, and after changing the mail server, load them again? The main thing is that these letters can then be searched. Thank you in advance for your response.

Answer 1

It is not entirely clear how much mail, the number of users, and how it is stored (locally or on the server), so it is difficult to give a correct answer. Perhaps using an imap server will help. Third party if it is not provided by the current servers. Those. just upload the current mail to the imap server, connect a new mailbox and move the mail there. It should work with any email client and the number of actions depends on the number of directories, not letters.
If both mail servers provide imap, then it should be possible to connect two mailboxes and simply copy/move all emails from one to the other.

Answer 2

For example,
oswatershed.org/pkg/imapsync ( https://github.com/imapsync/imapsync )
offlineimap.org