How to transfer corporate mail from Google Apps to linux mail server?

Question

Google Workspace

Greetings!
There is a corporate mail on Google Apps.
Finally, we bought a server for our own mailer.
Deployed iRedMail on Debian7.8: Postfix+Dovecot+MySQL etc.
The authorities want all mail to be transferred to the new mailer (and not downloaded to clients' computers).
How to do it?

Answer 1

There is a software from Google that pumps out all the mail from one mailbox to the archive. Tried - works. There are no links left - you will find it yourself .
How to upload to your mailer - I will not say.