Missing email and mailboxes after upgrading to Catalina on Macbook Pro

Hello, arm_oregon!

Thank you for using the Apple Support Communities!

If I'm understanding your post correctly, after upgrading to macOS Catalina, you are missing some mailboxes but you have a back up of this data in Time Machine.

If you made a Time Machine backup of your files before updating to Catalina, you can use the backups to restore those lost mailboxes and messages.

Take a look at this article from the macOS User Guide called Restore items backed up with Time Machine and follow the steps provided to learn how to restore these items.

I hope this information helps you!

Cheers.

G'day,

There is a solution at https://discussions.apple.com/thread/250970504?page=1.

If you still have a backup of /Users/<your user id>/Library/Mail/V<some number> from before you upgraded you may be able to recover your mail by following that process. (This backup should still be in TimeMachine if nowhere else.)

If you don't have that backup then have a look at /Users/<your user id>/Library/Mail/V7. If this is large then your e-mails are probably there and you may be able to apply the procedure to that. (I haven't tried this.) You want to apply it folders whose names are of the form <Hex number>...<Hex number> whose date is the day of your upgrade. Don't apply it to folders of that form of name whose dates are after the date of the upgrade because these are for your current mail accounts.

Good luck.