Interesting. I didn't know you could have Hidden Folders on Time Machine, so while we are writing about Hidden Folders on TimeMachine, that is what you are going to have to find.
Restoring Mail from a Time Machine backup requires navigating to the hidden user Library folder, where Mail data is stored, and then using Mail's import function.1
Important: Mail data is stored in a hidden folder, usually at ~/Library/Mail/Vx (where 'x' is a version number that changes with macOS updates).2 The standard Time Machine interface in the Mail app no longer works reliably for restoring individual mailboxes in recent macOS versions.
Steps to Restore Mailboxes
Close the Mail App: Ensure the Apple Mail application is completely closed.
Open Finder and Reveal Hidden Files:
- Open a new Finder window.
- Use the keyboard shortcut Command +Shift+ Period to show hidden files in Finder. You'll see several new, semi-transparent files and folders, including the Library folder in your home directory. Use this shortcut again to hide them when finished.
Navigate to Your Mail Data:
- In the Finder window, navigate to your user's Library folder: Your User Name > Library > Mail.
- Open the latest version folder, typically named Vx (e.g., V10 or V11).
Enter Time Machine:
- With the Vx folder open in Finder, Enter Time Machine (click the Time Machine icon in the menu bar and select Browse Time Machine Backups).The Time Machine interface will open, showing the Vx folder and its history.
Locate and Copy the Backup:
- Use the timeline on the right or the arrows to navigate to the date of the backup you want to restore.8
- Inside the Vx folder, you'll see folders with long alphanumeric names (these correspond to different email accounts and "On My Mac" mailboxes).
- Select the specific alphanumeric folder(s) you need to restore or, if you're unsure, select the entire Vx folder.
- Click Restore. When prompted, choose a location to copy the folder(s), such as your Downloads or Desktop folder, to avoid overwriting your current Mail data. Do NOT choose to replace the current files in your actual ~/Library/Mail folder.
- Import Mailboxes into Mail App:
- Exit Time Machine and open the Mail app.
- Go to File > Import Mailboxes... in the menu bar.
- Select the option "Apple Mail" and click Continue.
- Navigate to the folder you copied (e.g., in your Downloads folder) and select the specific alphanumeric folder(s) or the Vx folder you copied. Click Choose.
- The imported mailboxes will appear in the Mail sidebar under a new section called "Import" (often with a subfolder for the date/time of the import). You can then move the messages or mailboxes to your current account structure as needed.
