If you have made a backup (export) of your mailbox, you can easily import it into Apple Mail.
Follow these steps in Apple Mail:
- Via the navigation bar at the top you go to “Archive” > Import mailboxes … “
- Select the type of your backup and click “Continue”.
- Select the file with your backup and click on “Select”.
- After the import is complete, click on “Done” to complete.
- You can find your imported mails in the “Import” folder (see image).