How can I get Thunderbird to display emails that exist in the IMAP account's local INBOX file but are no longer on the server?

Question

This IMAP account is set up to keep all data both locally and on the server. A few days ago all emails in the inbox for this account disappeared from both Thunderbird and the server. (Since then the inbox, both locally and on the server, has started to get repopulated as new messages have come in.)

I have gone into my TB profile and used a text editor to look at the INBOX file for that account, and found that it still includes all those missing emails (as well as all the new ones that have since arrived). I tried to find the junction between the last of the "missing" emails and the first of the newest, and precisely at this point I found that data from about half a dozen emails from six years ago has somehow been copied here. (I have tried to remove this data, but that was tricky and didn't work.)

I tried to open the INBOX file with another mail reader (Mbox-Viewer), and it could read the entire INBOX file without a problem.

So I would like Thunderbird to read the entire contents of the local INBOX file, but I don't know how to do so. Because it's an IMAP account, will TB always look to the server to know what to display, even if there is more data in the local INBOX file?

Answer 1

A safe way to save and to view those messages, though there might be simpler ones:

1. Disconnect from internet and copy the entire profile folder, twice to another location to insure that updates from IMAP server do not delete mail, and to provide a profile for experimentation.
2. Try, on one of the copies, moving folders (e.g., imap.aol.com or imap.googlemail.com) from ImapMail to Mail\Local Folders.
3. Open Thunderbird and change the active profile to that of the modified copy.
4. All those messages should now be visible in separate folders under Local Folders. They can be exported, and then re-imported into the normal Thunderbird profile.