First, I am not understanding your primary issue. My grasp of your basic intent is to have thunderbird and accounts on drive C and local folders on external drive. Transferring to new computer would be to copy profile to new PC (which is now a simple menu option, thankfully) and then reset LocalFolders to point to the external drive. I don't understand the steps in detail on what you did, as it would be in the details should be clues on where the messages are missing. I will add that the definition of where Local Folders is stored is at account settings for local folders, not within 'copies&folders' for the account.

My inference is that your issue is to copy local folders from Win 7 to the new profile. A simple way, using WIndows FIle Explorer, is to rename the Win 7 Local Folders to something else and then copy the renamed folder to within the Local Folder on the Win 10 PC (while Thunderbird isn't running).

Although I don't know your full intent, something to consider might be to put the entire profile on the external drive. That would simplify backups as everything would be within one folder (accounts, addresbooks, messages, local folders).

Thank you for your fast reply, David. I see I wasn't clear. I have stepped through all the normal steps to move my local folders and when that didn't work, I also tried other folders where I thought the missing emails might have strayed.

This past year, my routine backups stopped saving to the backup drives where all Thunderbird from 2009 has backed up without issue so this has been a hidden problem for almost a year. Whether copying from the AppData folder or from the Profile folders saved in normal backups, I get the same result: old mail that stops in May 2022 with Inbox & Sent boxes showing current mail that hasn't been put in the Local Folders shown on the left side of the page. Since the old laptop shows the 2022-2023 emails in the Local Folders up until I stopped moving them there last week I know they are somewhere. on the Windows 7 hard drive. I have looked at all Local and Roaming and Profile folders File Explorer can pull up (these are some I tried copying and/or syncing to or with existing folders without any better results).

So my question is where else could these lost mails be?

I do realize that no one else can tell what I did wrong. I'm just hoping that someone can give me other ideas on how to locate them. My next step is to run a search for all .msf files in the hope of spotting some stored in some odd corner. If that doesn't work, I think I'm out of ideas. But thank you so much for your quick and what would normally have been a very helpful reply. Anne J

Anne, First, this tip: the greatest little freeware program for finding stuff is called 'everthing' and can be downloaded from this url: voidtools dot com. It's tiny and can find darn near anything in a fraction of a second. Unbelievable speed. Just type a few characters in and it starts. I wrote this, thinking of your comment about searching for .msf files. Scarcely a day passes but I don't use it several times.

Second, I encourage you to establish a simpler means of backups. Thunderbird's export to zip may not fit your needs, but the importexport addon has a nice one. If doing any other backup, it MUST be done when Thunderbird is not running. I have seen many posts here from people using proprietary backups that failed to restore, either because they reallocated data placement or they ran while Thunderbird was active. My suggestion is to put the entire profile together, whether on drive C or elsewhere. Since the bulk of the profile is messages, putting everything together makes a restore a simple step. Thunderbird needs to stay on C, but the profile can be anywhere.

Do keep me posted, as I want to see you escape from this situation.

Blessings on your head, David. Both of these tips sound like, if not lifesavers, at least frustration savers. I do keep Thunderbird on C and I do close all programs before running a backup.

I did round up the .msf files and found that many date during the "lost" time period and were filed in an adjoining folder for an account I use for things I handle for my daughter. I synced the main backup folder with this folder, crossed my fingers and then uncrossed them when Thunderbird refused to set the resulting folder for storage. The message: "A subdirectory of the directory specified in the Local Directory setting is already used by the "Local Folders" account. Please pick a different directory." I'm guessing that I'm going to have to tiptoe through the various folders for duplications and figure out how to streamline them. Either that or the current setting for storage, E:A\Anne\AppData,which has nested within it a couple of Local Folders is also cross referencing with this latest storage folder attempt. I think I might have done too much putting together of files in an attempt to add the missing to the always there mails but since they're all there...somewhere...I'm hoping this knot can be untied and straightened.

Thank you again for your interest and suggestions. AnneJ

PS...that file of my daughter's is another Thunderbird folder of saved emails, not extraneous business records.