Open TB, Help/Troubleshooting, Profile Folder, Open Folder, close TB. Open the Mail/Local Folders location. In the profile on the old drive, open the Mail/Local Folders location or account subfolders of Mail, e.g. Mail/pop.gmail.com, and look for the mbox files, which are large files with no extension, named after folders. Copy the mbox files from the old profile into Mail/Local Folders on the new computer, then restart TB and find the folders under Local Folders in the Folder Pane.

I followed your instructions, I believe, correctly, but after rebooting and restarting, TB still doesn't recognize the files in Mail/Local Folders that I copied there, even though they are appearing in the Profile accessed through the Troubleshooting menu/open folder. When I open TB, I note that I am taken to a screen from which I must select the correct profile (2 appear from a previous attempt...I thought it might be preferable to access the old Local Folders from a different profile, but I can't do that because set up stalls when I'm prompted for a password. I could possibly delete the 2 other profiles which aren't operational anyway, but I'm wondering if I might screw something else up by doing that. I'd also love an explanation for why the moved Mail/Local Folders from the old program aren't being read in TB on the new computer so as to appear in the drop down menu for the Local Folders icon on the working account.

I can't say why the mbox files from the old profile aren't recognized in the new profile. Perhaps post a picture of File Explorer showing one of the mbox files in its current location.

I'm attaching the requested screen shot, never done that before on this computer...

Does it help?

Did you copy just the mbox files or the .msf files as well? The dates on the .msf files suggest they were not created in the last few days. Try deleting all .msf files, then restart TB.

An easy way to make screen captures is with the Snip & Sketch app (Winkey+Shift+S).

Deleted all msf files, closed Thunderbird, restarted Thunderbird, still not reading files in Local Folder located in Mail folder in the working profile. To double check, I rebooted and again restarted TB, but again no read of the local folders or files. I am assuming that these files do not need to be in a like-named folder in the Local Folders folder, and the Local Folders folder can be read if it resides in the Mail folder. Is that correct?

In the profile Local Folders folder (which resides in the profile Mail folder), in addition to other folders which appear to correspond to some, but not all of the named local folders, I note in the Local Folder folder the presence of two other files, namely “filterlog” with a Microsoft Edge icon, and msgFilterRules, a DAT file. I am guessing that they should remain??

I am also still wondering about the wisdom of perhaps deleting at least one, if not both, of the profiles which appear to be inaccessible for lack of a stored password.

And thanks to you for sticking with my request...I’m sure you can appreciate my sense of frustration. The replacement computer seems to be working much better, meaning faster, for most all tasks, than the one that crashed, and restoring access to the archived mail in the Local Folders will pretty much end my migration journey, if only we can find a path to getting TB on the new computer to read the Local Folders folder from the Mail folder copied there from the old profile.

New topic: Is it possible that an inadvertent change of password could be problematic? On the older computer, I had been using a master password which provided access to two mail accounts and all other folders, plus two different smtp out passwords, one for each of two separate mail address accounts. At this point, I am only interested in retrieving the Local Folders set up for the primary account.

Final thought: I may be wrong, but I believe my mail protocol on the old computer was smtp, but on the new computer the profile identifies IMAP. Could a mail protocol discord be a source of the problem, as I believe the old downloaded mail was resident on my computer, but I believe that IMAP leaves incoming mail on the server? If TB on new computer is looking for local folders on the server, rather than on the new computer after being copied there, maybe that's why they are not being read?

Sorry for my lack of brevity, and thanks again for your help.

Did you close TB before deleting the msf files or after? They must be deleted while TB is closed.

The mbox files should be copied directly into Mail/Local Folders, not a subfolder.

The filter log and dat file are normal and do not affect the folders, and the lack of a password for one profile doesn't affect the others.

If TB was compacting folders or the mail folders were being scanned by antivirus when TB crashed, it may have corrupted the folders to make them unreadable. If that's the case, you will have to restore from a backup profile, if you have one.

SMTP is the protocol for sending mail, while POP and IMAP are the protocols for receiving mail, and I don't think that would affect the ability read mbox files in Local Folders.

I'm not sure whether or not I closed TB before deleting files , but the filed I deleted do not appear to still be there. Are you saying that if they were deleted while TB was open, the delete would fail? If so, why would they not be visible in Explorer, which they at present are not?

There were some sbd files in which there were lingering msf files, so following your most recent suggestion,I opened the profile, closed TB, deleted the remaining msf files, and then reopened TB, but I am still not seeing in open Thunderbird the local folders which are resident only in the Local Folders folder of the Mail Folder in the subject profile. I will post this, close TB, reboot, and try again, but based on past difficulty, I am discouraged that the local folders still will not be visible to TB.

Because the data on the old hard drive remains accessible, I can again recopy files from the old profile Mail/Local Folders to the current profile Mail/Local Folders. If simple reboot after I post doesn't work, I would take the time to repeat that step if you think it has a fair chance of being successful. My rationale for doing so is the possibility that I tried (and from the file read in Explorer, was successful) in deleting the msf files as you had recommended, even tho' it is possible, even likely , that I failed to close TB before beginning the delete procedure. I hope you will respond to this. I will update if I have success. Thanks.

So rebooting after removing a few remaining msf files from the Mail/Local Folders folder was not successful. Next step is to trying to repeat copying the backed up Mail/Local Folders files I want from the old profile into the troubleshoot/open folder Mail/Local Folders in the working profile on the new computer. I will report success but would still like some help should I be unsuccessful.

As contemplated yesterday, today I followed these steps: Open TBird, Help, Troubleshooting, Open Profile, Close Tbird Open backup drive; ....App Data/Thunderbird/Roaming/profile/Mail/Local Folders Selectively copied files, one by one, from Local Files backup to existing Tbird Open Profile/Mail/Local Folders, replacing existing copies in the open Profile Closed Explorer window to which files were moved Restarted Tbird In Tbird, Under Local Folders, no appearance of any of the copied filed (sigh)! I am disinclined at present to reboot (have some stuff to attend to).

Any further suggestions on how to make my archive of old Local files accessbile? I'm stumped and frustrated, as the problem for which I sought help remains unresolved.

There are a number of free and commercial programs to repair corrupted mbox files, such as this one, but I have no experience with any of them. Note that mbox files can be opened in a text editor, in case you need to view critical messages.

Thanks for pointing this program out to me. For the purposes of accessing the old Local Files, it works admirably. I truly appreciate your help and patience.