You know it is hard to get a simple answer to a simple question.

But this is not a simple question. Thunderbird starts by storing your profile in a random location, Then it stores mail in separate locations if the account is IMAP or POP.

But given that IMAP is completely synchronized with the mail server, why would you think you can restore them from a backup. The backup will simply resync and you will be exactly where you are now. Where ever that is.

Perhaps you might explain exactly what the issue is, because it sounds to me like you are not going to do more than get frustrated with whatever you are planing on doing.

Comcast locked up for a day, when it began working again, my sent folder was empty. Yes I know IMAP does a synch. I run regular backups (3) and was hoping to restore the sent folder from a backup. I've looked under the IMAPmail directory and while the files exist with contents they're not restoring.

Restore them somewhere else like you desktop. Then use the import export tools addon to import the files to the Thunderbird "local Folders" account.

From there you may be able to move them to the original location and have the sync work in your favor. But batches on more that a few hundred may not sync properly.

At the end of each year I archive the current year's sent folder to it's own local folder so your approach is a very good one. Many Thanks Matt!