Google Takeout: Import MBOX file with Apple Mail

After Apple Mail is configured with the account that you are moving messages to, you will be able to import the MBOX exported through Google Takeout. For instructions configuring Apple Mail, go to Apple's webpage: https://support.apple.com/guide/mail/add-email-accounts-mail35803/mac in Apple Mail.

Once configured, follow the instructions below to import the downloaded MBOX:

Select File > Import Mailboxes.
Select Files in mbox format and then click Continue.
Browse to locate the mbox from your Google Takeout download and click Choose.
The mbox will be imported into a local folder in Apple Mail. It will be located in the Import folder under the heading On my Mac.
Select all the messages in the imported folder and then drag and drop them to the corresponding folder in your destination account.
Repeat these steps for all exported mbox's.