In Mail program, local archive folder disappeared

Thanks Eric, this was very helpful.

This is so interesting. I followed your directions, selected Library/Mail, but instead of opening Time Machine, I clicked the Mail folder, saw folder V2; clicked that and saw folder Mailboxes; clicked that and saw Archive.mbox; clicked that and saw INBOX.mbox; clicked that to see my missing archived folder ⚠, so it IS there in the Mail Library. I clicked that archive folder and saw another folder with a long serial number name to the folder (1EEE924A-10DB-4 . . .); I clicked that and saw folder Data; and so forth until I found several clicks later what appears to be the message files (.emlx).

As I can see this archived folder in Finder, it appears that I do not have to go into Time Machine to restore. Is there a way to get these files visible again in my updated Mail program?

Eric- I almost have this problem licked, but not quite.

Instead of copying emails to folder on Desktop, I created a new folder within ON MY MAC calling it Archive- [dates- from-to]. That moved successfully from my IMAP freeing up needed space, so I can breathe a little now.

I don't want to delete the previously existing archive folder in the user library because then I will lose my archived data.

Here is what I discovered. The "lost" folder is not in the ON MY MAC folder, but in an erroneous sub-folder, that I had named INBOX. (I will delete that later) I moved the "lost" archive folder from INBOX to the Mailboxes folder, (the same folder as my newly created archive folder that appears under ON MY MAC. I closed the Mail program, then reopened it, and just as I hoped, the lost folder appeared within ON MY MAC. But the trouble is, there is no DATA, that is, no archived emails, that can be seen in the Mail program, yet, the data does exist in the Finder sub-folders.

I then tried to import this mailbox with File > Import Mailboxes, but could not find the Mail folder. It was not listed as a sub-folder within Library! The folder list went from "Logs" to "Messages", skipping "Mail" and "Mail Downloads" folders. They were not there! Weird, eh? If I could import the archived folder into Mail from the ON MY MAC folder, I think my problem will be solved -- that is, the data would be imported and the archive would be seen. How can I import this mailbox if the Mail folder is not even visible from the directory within Import Mailboxes?

Thanks for your help with this dilemma!

This is a follow up to my previous post. I was able to find the Mail folder within Mail program File > Import Mailboxes. I got in through Users > and clicked through until I got to the Library > Mail. I found the lost archive within the ON MY MAC directory, where I had move it, but the import did not work. I tried to import via Files in mbox format, but got an error message, "No valid mbox files were found".

Any ideas how I can get the data to be seen in Mail program?

Got it! I figured it out! I was trying to import the files using Files in mbox format. I just tried importing using Apple Mail, and it worked! I guess I can't get credit for solving my own question, can I? :-)