For my wife I set up a “new (to her)” 2014 Retina iMac with a 1TB SSD to replace her old 2009 iMac with a spinning HDD. Everything is fine and all works well except that the “On My Mac” mailboxes, where she manually saved certain emails from friends, from the old 2009 iMac are not present on the “new” iMac and cannot be found on the TM or CCC backup disks (see picture below).
Here is pertinent background:
Old iMac: late 2009 iMac running High Sierra, 1TB HDD. External backup disks were made using Time Machine and Carbon Copy Cloner.
“New” iMac: 2014 Retina iMac with original Apple 1TB SSD. Previously was my iMac, running macOS Mojave, no problems. Set up for my wife by erasing SSD, formatted with APFS and “clean install” of macOS Mojave. Then I manually transferred data files - Documents, Desktop, photos (Photos Library.photoslibrary), Music, Movies, etc. Her iCloud, Mail, Dropbox and 1Password accounts were installed/set up without problems.
How can I recover the “On My Mac” mailboxes (“.mbox” files) from the old 2009 iMac? These are of course not present on the IMAP servers for her various email accounts.
After some digging around in my new 2020 iMac, I found the expected location of the “On My Mac” mailboxes (".mbox") files, located in the macOS “hidden” library folder: ~Library>Mail>V7>41E054EB- … (see attached photo). Apparently I should have exported these mailbox (.mbox) files from the old iMac’s Mail app, then import them into the new iMac’s Mail app. But I didn’t think ahead to do that
Apparently neither the TM nor the CCC backup disks contain the “hidden” library folder (see attached photo). A different library folder is present in the TM and CCC disks, but not the needed “hidden” library folder.
I still have the old 2009 iMac, but it is not usable because the 30-pin screen connector on the system board is broken. You can probably guess how this happened, but I won’t tell unless someone asks )
I suppose I could remove the disk drive from the 2009 iMac, mount it in an external drive enclosure and access its data on my wife’s iMac or on my iMac. Would that method allow access to the “hidden” library folder? And is this necessary, or can I find the hidden library folder somewhere on the backup TM or CCC backup disks from the 2009 iMac?