Combining multiple Google Apps accounts, transferring email databases?

Question

Google Workspace

There are 2 domains on which different accounts are configured in Google Apps. There is a need for both domains to be linked to the same account.
Google writes that this procedure is not supported. Is it possible to transfer user mail databases with all data and labels to one account by some third-party means?
The number of users on one domain is 13 on the other 10, so even if you have to do something manually, this is not critical.

Answer 1

As far as I understand the essence of Google Apps, only one mail service can be added to one account. If you want to transfer only the mail (letters) without saving the addresses. That can be done through IMAP.
To the mailbox that needs to be transferred to another account, you need to configure a mail client like Thunderbird and pull all mail through it (via IMAP) to a local folder.
Then, in the same mail client, add a second mailbox (from the second account) to which the move is being made. And just shift the mail from one box to another. Thus, everything will “flow” automatically.