"On My Mac" email

Some of it may be in ~/Library/Mail/. That is, ~/Library/ as in your user-level Library folder, not /Library/ as in the system-level Library folder.

The Finder has been hiding the user-level Library directory for a while. If your old machine was still working, you could get to it by holding down the Option key while using the Finder's Go menu. That would add Library to the menu. If you're mounting the old drive on another computer, as a second/external drive, you'll probably be able to go to that directory directly.

Note that the file and directory structure in there is clearly arranged for the benefit of a program and not for the benefit of a person trying to access the files directly.

Found this (among other articles) on the Web:

https://www.askdavetaylor.com/how-to-transfer-apple-mail-folders-to-new-mac-system-import-export/

All you emails should be on the web server unless you deleted them.

Have you tried a Spotlight search? Mail messages I see are all type .eml. Even those saved to a non mail folder for safekeeping.

Maybe some clues here:

To access the "On My Mac" email folder on a Mac, users can follow these steps: 1. Open the Mail app on the Mac. 2. Click on "Mailbox" and select "New Smart Mailbox Folder." 3. Enter a name for the folder and click "OK." 4. Drag one or more Smart Mailboxes into the folder. 5. When viewing the folder, emails from the Smart Mailboxes that the folder contains are shown. 6. To delete a Smart Mailbox, select it in the Mail sidebar and choose "Mailbox" > "Delete Mailbox." 7. The emails that were listed when you viewed the Smart Mailbox are not deleted. 8. To move and copy an On My Mac email folder to a new computer from one Apple Mail for Mac installation to another, open the folder you want to copy under On My Mac in Apple Mail on macOS. 9. If you're importing a mailbox exported from Mail or a folder in the /Library/Mail/ folder on another Mac, select Apple Mail.0

I believe you use File / Import Mailboxes… to import the old data to a copy of Mail running on another Mac. (That is, if you're running the same version of Mail, or a later version of Mail, on that second machine. If you're trying to take mail back to an older version of the Mail application, the version of the mail data might not be one that it was programmed to understand.

@ku4hx

Is it possible to somehow get mail from the web server to the Mail app on the computer. Since the server settings changed on my computer mail app there are lots of emails on the server that were dropped from Mail on the computer.