How to transfer mail and mailboxes from hosting to a local mail server?

Question

Email

Good afternoon, we have encountered a problem that seems banal, as it seems to me:
- there is a reg.ru hosting on which our site is spinning
- on the same hosting we have a mail where letters arrive

Recently, the place on the hosting has run out and, accordingly, the mail stopped working.
We have our own internal server with an external IP, on which, in principle, we can also raise a mail server, but the question remains how to migrate correctly so that the addresses remain the same, but everything is stored on our internal server and, accordingly , did not take up space on the hosting.

I would be grateful if someone could share their experience of similar moves.

Answer 1

Understand correctly, reading your question it becomes clear that you do not understand how it works at all and unfortunately, this whole "project" will only bring you unnecessary problems.
You have 2 options:
- Hire a specialist who will complete the migration over the weekend
- Move to Gsuite (or Yandex Mail for Domain), they have their own means of migration from regular mailers.
If you still want to go on this adventure, then so be it.
Set up your mail server (you can do it on the basis of iRedMail / Zimbra, manually using thousands of articles on the network, or even just by installing a hosting panel, for example VestaCP, it also includes a configured mail server, just like on hosting)
Create the same accounts on this server records as used on hosting.
Change the MX record in the DNS of the domain to the external address of your server (now letters will be sent to it).
Start transferring old user letters. It can be done in several ways:
- Manually (by connecting via ssh to the hosting server, just copy the email files via scp to your new server)
- Automatically, using the imapsync utility
- Manually "in a simple way" (if there are few users, you can transfer all emails without straining using an email client, just take Mozilla thunderbird, set up an employee account in it on the old server and on the new one, drag letters from the old account to the new one, they will be transferred to the new server).
Also, don't forget that the ISP that gave you the external IP must set a 'backreolve' record for your IP containing the server's domain, otherwise 90% of emails sent from this server will go to Spam.
After everything settles down, it’s worth reading in the direction of DKIM / DMARC and be sure to take care of backups.

Answer 2

If I understood correctly, then the question lies in the overflow of mailboxes on the hosting.
I think the easiest option is to supply users with email clients that pull letters with deleting copies on the mailer (hosting), thereby clearing the space.
I think it will be easier than fussing and setting up a local mailer.

Answer 3

Collect the machine responsible for the mail. And more disk space. Trying to hosters how to drag mail from their server to yours. Rebuild all DNS records responsible for mail (mx dkim spf dmarc).