POP mailbox on Macbook Pro

Excerpted from Create or delete mailboxes in Mail on Mac - Apple Support:

WARNING: Deleting a mailbox permanently deletes the mailbox and its contents (including other mailboxes), and can’t be undone.

Apple very rarely calls attention to what they say with ALL CAPS and boldface. When they do, it's important.

There is hope though, at the end of that passage:

Note: If you set up Time Machine to back up files on your Mac, you can use the backups to restore content that Mail downloaded (based on options set in Mail and on your Mac). See Restore items backed up with Time Machine.

"POP mailbox on Macbook Pro: Deleted the mailbox. How to recover the emails."

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Recovering Deleted eMails:

Where to Look:

Check your Deleted and Archived folders.

Export from Another Device:

Boot up another device associated to this account, making sure it does not connect to the internet upon boot (perhaps powering off your router?). While WiFi is off, try exporting your mail. Then, import them once all is backup and syncing.

1. Go Here: Import or Export Mailboxes in Mail on Mac - Apple Support.
2. Scroll to: Export mailboxes
3. Proceed from there as necessary.

Arlando Keith wrote:

Deleted the mailbox. How to recover the emails.

Recover the emails from your backup.