Assuming you have done this because you are using POP and are referring to the default Archives folder, there should be a folder called Archives.sbd in the email account folder (named pop.gmail.com?), containing all message files and corresponding .msf files (though the .msf files can be rebuilt and are not vital to keep). In fact all "real" folders created under Inbox in Thunderbird should have an .sbd folder. See this page for more info.

Make sure that locations under Keep message archives in under the Message Archives section under Tools > Account Settings are also valid.

Files under AppData/Local are cache files and may be system dependant. Therefor I’d not recommend to copy those from another profile - just the content under AppData/Roaming would do. Theoretically you should only need to copy and replace every file and folder under the (old) xxxxxxxx.default profile folder - only the new profile folder name would be different, if created by Thunderbird. You could also do this and include the profiles.ini file in the AppData\Roaming\Thunderbird\ folder, after which the setup should be identical.

Does this help?

Thank you. I'm completely unfamiliar with the inter-workings of email or its conventions. Your first linked "this page" appears to say that folders can't be copied to an IMAP account and only a POP account. You assumed POP too. I originally was using a POP account but switched to IMAP about a year ago (on the old computer). I set up the new installation of Thunderbird as IMAP on the new computer. Should I uninstall and reinstall to set up a POP? Also, I searched the old HDD for all "archive" files and there was only a "no extension" and an .msf. There was no Archives.sbd.

Correct, the file and folder structures for POP and IMAP aren’t similar, so they can’t be converted. Now it seems you previously created a folder called Archives yourself, so this is not about the default Archives folder, correct? In that case it might be 2 files called Archive and Archive.msf. Do you recall where the archives were saved, such as under Local Folders?

Now I’m not very experienced with IMAP but if you were using it before and just want to continue doing so like on the old system, you should just as well be able to copy/move the entire backed up profile and have everything set up, including any local folders/archives. I always used this method and even for the full folder instead of by copying particular files, though there were no IMAP accounts set up at the time I last did.

Also, since IMAP works in a way that you are actually always looking at a synced copy of the server’s content, any folder you have stored locally should also be available on the server, except for the Local Folders content, residing in the Mail subfolder (For IMAP, all mail content is in the ImapMail subfolder.) This is why you better not uninstall and reinstall (or rather: not set up the account again, since TB reinstalls do nothing with profile data) to set up POP in order to get the messages back, as you might accidentally delete them rather than finding them back.

The only thing to check would be the Local Folders setting - Right-click on this folder in the left pane, choose Settings, look at "Local Directory:" and check whether the path matches the new ...\xxxxxxxx.default\Mail\Local Folders path you see there. If you did copy over the backed up profile, chances are it does not match.

If you were to copy/use the full backed up profile, you could open the restored prefs.js file, look for any entries containing the old profile folder name and edit them to match the new one before starting Thunderbird.

So in short, do you still see the missing content when using webmail? If not, I’m afraid it would be lost, though it just should be available in your backup, providing you backed up the full profile folder of course. Theoretically you could have set up the Local Folder location on a different disk and even outside the profile folder, in which case they are not inside the backup, but I’m not entirely sure if that should work.

As for backups, it’s always good to check whether a backed up copy actually works and/or has identical files. Also avoid using MozBackup, since unfortunately it is no longer supported and may cause missing files.

I would probably create an additional profile using the Profile Manager as explained in the support article (allowing to choose from at startup), exit and do a 100% copy of the backup there. I would not copy the AppData/Local files, and probably delete all *.msf files in the profile.

I only archived using the "archive" button on Thunderbird's user interface. If it was set up on the old computer like it currently is on the new one (same defaults) then it appears the Archive button put the "archive folders" under the email account folder (with Inbox, etc.) , not the Local Folders. This is from the prefs.js file: user_pref("mail.identity.id1.archive_folder", "imap://******@imap.cox.net/Archives"); So it looks like it's pointing to the imap on cox.net / Archives "folder". However, when I look at my email "directly" using webmail, there is no Archives folder, just inbox, trash, sent, etc. Now, looking at my files / folders associated with my profile further via Windows File Explorer, I see there is an ImapMail/imap.cox.net/Archives.msf file. There is no other "Archive(s)" file in that folder. However, it's the Mail/pop.cox.net/Archives.sbd folder (not file) that has multiple .msf files and "no extension" files, all named by years (2007, 2008 ... 2016) in it. That's the structure of what I was looking at in Thunderbird under Archives - what I'd like back. In fact, I don't know that I "archived" anything (with the button in Thunderbird) after switching to IMAP from POP. I didn't see any POP references in the prefs.js file - only to IMAP. Is there a way to point Thunderbird towards the archive-related files instead of the IMAP file (which probably is empty)?

For comparison:

If I move a message from a POP account’s Inbox to the (previously empty) Archives/2016 folder in Thunderbird under that account, the message is copied to the Mail\pop.xxxxxx.com\Archives.sbd\2016 file, and its corresponding 2016.msf file is updated. When moving it back to Inbox (and after compressing the archive folder), the 2016 file gets back to 0 bytes, and its .msf file remains a few kB.

If I do the same for an IMAP account that has a default "Archive" folder, the similar happens with the Archive and Archive.msf files. It also needs to be compressed afterwards in order to really clean up the Archive file and bring it back to 0 bytes, the .msf remains a few kB.

In fact, I don't know that I "archived" anything (with the button in Thunderbird) after switching to IMAP from POP.

Would that mean you are only looking for the automatically archived messages for your POP account? I presume they should be in the 2007, 2008, ... 2016 files (the "no extension" files), and you could skip searching the IMAP Archive file in that case. Do I understand you still do have them and if so, did you look at their size? You could even view them using a text editor or other viewer - it's plain text after all.

If you found an Archive.msf for the IMAP account/folder, that would mean there should be an Archive file as well with some size other than 0 bytes, unless you never actually used it for IMAP. The fact you don’t see that folder using webmail may be proof of that.

Now in order to view the POP account’s Archive files and folders in Thunderbird, you would need to have a POP account set up there. That could be any POP account and set up successfully or not, and you could copy the 201x... files to the appropriate folder using the explorer. An issue would be that when setting up a new account, an Archive folder does not exist, but you could probably create it manually and drag the files there using explorer - I haven’t checked though and would not recommend it.

Instead I would prefer copying the entire old profile to a newly created profile’s folder. Is there any reason not to? I just tested again and everything including the Archive content is just copied and visible. Or was the POP account already removed in Thunderbird, despite its references still present in the prefs.js file? (I think it wasn’t since you could still view its Archive files.)

An easy way to create a new profile nowadays would be to choose Help > Troubleshooting Information > click about:profiles > Create a new profile > Finish. This will only create a default set of files and add an entry for the Profile Manager that should start from then on when launching Thunderbird. Exit and then remove all content in the newly created profile folder and put the backup copy’s content there, after which everything should work, even before checking/changing some path settings after launching.

Of course you could also set up the same account as POP within the same profile if it was deleted (be sure to leave messages on server then). As soon as the archives are visible, you should be able to drag messages to the IMAP account as described here. Note however that the Archive folder for IMAP should reflect an archive on the mail server too and not a local folder, so moving them under Local Folders in Thunderbird would be better.

There is one thing that should be mentioned before trying all this: check to make sure that "View -> Messages" and "View -> Threads" are both set to "All", since sometimes messages can be hidden in other views. I sure don’t hope (or perhaps I do) this is your only issue. ;)

Btw, it would be good to edit your post above to remove your username.

Thanks for the last tip - I'm such a newbie! I also confirmed the View -> Folder and View -> Threads are set to "All" I didn't see a "Messages" under View). I've looked at the files under Archives.sbd under the POP folder and they're full of what they should be full of. I don't have any "no extension" archive file in the IMAP folder, nor do I have such a folder in the email account itself (as viewed by webmail). I've already copied everything under the default profile from my old HDD to under the new default profile on the new computer's HDD and, again, the stuff that should be under the new profile, is. I'm going to say for sure now that I haven't archived anything since I switched the email account from POP to IMAP, in other words, all of the archived files were archived when it was a POP account. Should I just go back to POP? Will that "bring them back" within Thunderbird? I like IMAP better for coordinating deletes, etc. as emails show up on whatever device / computer I'm looking at. Can I edit the user_pref("mail.identity.id1.archive_folder", "imap://******@imap.cox.net/Archives"); line in prefs.js to set the archive folder to the POP folder, the folder under my profile on the computer (as opposed to identifying the folder (if one exists) within the email account itself (with the "pop://******@pop.cox.net - I think that's what the imap string is doing with the @, etc.)? Would that effectively put / keep my archives "on my computer's HDD"? That'd be OK with me if it worked.

Should I just go back to POP? Will that "bring them back" within Thunderbird?

Well, you could do so, at least temporary, i.e. you could set up the account again for POP while retaining the IMAP setup (be sure to leave messages on server in the settings). As soon as you are done, you could use the Archive commands in Thunderbird to have the folders created automatically for each year, at least if you still have some older messages in the Inbox from those years. If you exit Thunderbird then and overwrite the content of the Archive folder, one should say the content must be visible. On the other hand, the folder structure isn’t magic so setting it up would be a bit overkill, but at least you are sure the account is properly set up even though a copied profile should work, and it could do no harm.

Can I edit the user_pref("mail.identity.id1.archive_folder", "imap://******@imap.cox.net/Archives"); line in prefs.js to set the archive folder to the POP folder, the folder under my profile on the computer (as opposed to identifying the folder (if one exists) within the email account itself (with the "pop://******@pop.cox.net - I think that's what the imap string is doing with the @, etc.)?

I don’t think so, as the IMAP setting basically belongs to a different (type of) account. Since this affects archived messages for the POP account, you should (have) set that up and find a separate entry for it. Additionally and IIRC, these entries are local for POP, but remote for IMAP. I see no pop:// entry in my prefs.js, but it would probably use mailbox://.

Now it’s currently not clear to me if you had the POP account set up prior to or after copying the old profile content, or did you remove it at some point? If you still have it or set it up again, things might be easier.

I just tested this: my Archives folder in Thunderbird only contains empty folders named 2009, 2010, 2011, 2012, 2015, 2016, which are actually 0 bytes sized files in the Archives.sbd subfolder on disk, and their associated 2-3kB .msf files. Guess what happens when copying a 0 bytes 2012 file to a file called 2014? It shows up as new empty 2014 folder in Thunderbird, and an .msf file is created. When copying a Trash file there that contains 1 message from the profile folder to 2014, a 2014 folder with the trash message appears. That means you should see anything you put there, as long as it’s a mail file in proper format. Maybe you could fiddle a bit with that?

In any case, make sure to check and properly set Tools > Account Settings > Copies & Folders for the Archives. If that doesn’t match, TB will never know where to look for them. I should have mentioned that earlier.

Fixed! I fiddled with copying files and folders as you suggested. In this case (essentially trying to revive emails previously archived as POP server emails into Thunderbird that's now set up as working with an IMAP email server) I did the following: First, I changed the location of the archives from the ******@cox.net folder to Local Folders using the Account Settings => Copies & Folders interface. Then I archived a recent email into the Local Folders to create the Archives.sbd in the Local Folders folder under the *default profile*/Mail folder. Checking the results with File Explorer, the new folder was there and was populated with a 2017 set of files (the "no extension" and .msf files) for the recent email I archived. Then, back in Thunderbird, I used the "New Subfolder" function (by right clicking the new Archives folder under Local Folders) repeatedly to create new folders named 2007, 2008, etc. to 2016 to match the names of the archived file sets that I had under the Mail/pop.cox.net/Archives.sbd folder that were copied from the old HDD when "transferring to the new profile." (* This "New Subfolder" step may not have been necessary - see next paragraph.) Then, after closing Thunderbird, I copied all of the 2006, 2007, etc. to 2016 file sets from the pop.cox.net/Archive.sbd folder (which were previously copied from the old HDD) to the Local Folders/Archives.sbd folder using File Explorer. I turned Thunderbird back on, looked, and there they were - fully intact - attachments and all!

I previously tried doing almost the same process, with the Archives folder being under the ******@cox.net folder in Thunderbird instead of the Local Folders folder AND without using the "New Subfolder" within Thunderbird to create the 2006, 2007, etc. to 2016 "folders." That did not work. Although the 2017 file set remained in the Archives.sbd folder from archiving a recent email to create the Archives.sbd folder in the imap.cox.net folder, all of the other file sets copied from the pop.cox.net/Archives.sbd folder via File Explorer not only didn't show up after opening Thunderbird and looking, they apparently were deleted by Thunderbird (or moved back into the pop.cox.net folder) and disappeared from the File Explorer interface under the imap.cox.net folder. I don't know which was key, using Local Folders instead of the IMAP folder, or using "New Subfolder" to first create new subfolders under the Archives within the Local Folders in Thunderbird. Interestingly, the "New Subfolder" function didn't really create new folders within the Archives.sbd folder, just new file sets (as viewed by File Explorer). I copied over these in the working sequence (first paragraph). In this "didn't work" attempt, I copied to the Archives.sbd folder under imap.cox.net without writing over anything as there wasn't anything to copy over. But the result would be the same - sets of files copied from the pop.cot.net/Archives folder. That being said, it appears that I probably didn't need to use Thunderbird to create the "new subfolders" within the Local Folders/Archives folder as those were copied over via File Explorer anyway.

Thus, I suspect it was the use of the Local Folders as the location for the Archives that was key to Thunderbird being able to read and display the emails previously archived when I was using the POP server, with the current IMAP server and settings in place. It seems that Thunderbird won't show POP archives when set up as IMAP (and perhaps vise versa?), at least not after being freshly downloaded onto a new computer, and in fact will delete the mismatched archive files (or move them back to the POP folder that it's not reading), but that Thunderbird doesn't care about the POP to IMAP difference if the Archives are in the Local Folders.

So really, it seems the issue would have been better characterized as asking about how to see archives previously created under a POP server set up while using an IMAP server set up (or perhaps vice versa) instead of how to retrieve archives from a profile on an older computer / HDD for use on the new profile / computer. Or perhaps these issues go hand in hand in this scenario. I don't know if Thunderbird would have the same issues with the POP vs. IMAP archives if it wasn't for the old computer dying, which necessitated a fresh download and installation of Thunderbird on the new one. Feel free to contemplate further. I'm just happy I have my archives back!

Thanks for your help!

Good, I hoped you would succeed. :) Interestingly I wrote a small addition to the previous post that wasn’t posted, awaiting your reply:

Something I forgot to mention or may not have been clear about: in addition to checking the setting for Local Directory: under Server Settings for each account, make sure to do the same for the folder called Local Folders either using right-click > Settings on that folder, or by going to the the bottom of the left pane in Account Settings.

I wasn’t convinced about whether or not you used the Local Folders previously, though looking closer at your first post, it looked like you did. I never used them myself so gave it little attention, and perhaps the other mentions of Local Folder may have been a little confusing. But if that’s the location where you had all archives stored, of course that location needs to match. Given that you wrote "it's the Mail/pop.cox.net/Archives.sbd folder (not file) that has multiple .msf files and "no extension" files, all named by years (2007, 2008 ... 2016) in it", (this appears to resemble my setup), that would indicate you didn’t keep them in Local Folders but the POP account’s subfolder. Unless this can be explained by using a Global Inbox or not, which would mean you would have all the POP account’s folders residing under Local Folders in Thunderbird instead of its own folder structure. You could check that using the Advanced button in Server Settings for the POP account.

Another thing that may be important is that old path entries in a (copied) prefs.js file do not get updated properly and without a warning (!), even though they appear to do so in TB’s settings when viewed only (and clicking Cancel). Apparently OK needs to be clicked on to store them in the file, so you’d need to do so for every dialog containing a path entry after copying a profile. See [3] in this bug comment for that - I wonder if that would mean such a setting and hence the Local Folder content is ignored in some way. The issue should also become clear when viewing prefs.js - every archive or other folder related setting should of course point to a proper path.

In addition to that:

First, I changed the location of the archives from the ******@cox.net folder to Local Folders using the Account Settings => Copies & Folders interface.

So you selected another location in the drop-down, perhaps even by means of the "Other:" option? Although it is not recommended to change any folder paths from within the UI, you now basically have set the per-account archives folder setting to use the Local Folders. It is not necessarily bad, but odd perhaps. The substep may not have been required allright.

Then, after closing Thunderbird, I copied all of the 2006, 2007, etc. to 2016 file sets from the pop.cox.net/Archive.sbd folder (which were previously copied from the old HDD) to the Local Folders/Archives.sbd folder using File Explorer.

If they were really in pop.cox.net/Archive.sbd previously, they should have appeared under Archives in the POP account that you don't have, provided that TB knows its location. But since you wrote they were in Local Folders on the old system, the question would be why the backup did not have them under Mail/Local Folders/Archive.sbd, unless the setting you changed to make it work was also changed on the old system and ignored on the new one (in the prefs?), I’d think.

I previously tried doing almost the same process, with the Archives folder being under the ******@cox.net folder in Thunderbird instead of the Local Folders folder AND without using the "New Subfolder" within Thunderbird to create the 2006, 2007, etc. to 2016 "folders." That did not work.
It seems that Thunderbird won't show POP archives when set up as IMAP (and perhaps vise versa?), at least not after being freshly downloaded onto a new computer, and in fact will delete the mismatched archive files

The Archives folder, or the Archives.sbd folder? Regardless of that, the issue may have been that you did not have the POP account set up and hence the associated Archives location was just unknown compared to the old system. Whether or not it was part of the POP account’s Archived folder or Local Folders previously, you would need to move them to Local Folders allright if the POP account was not set up or removed.

The Local Folders folder itself always resides locally (hence the name), so that folder is stored under the Mail folder in a file explorer, similar to other POP and Feeds folders if you use any, i.e. the Mail folder is for local content, whereas the ImapMail is about Imap and thus remote content only, including its Archive folder residing on the server and locally allright, but as part of the account’s content. IMAP can use the Local Folders, perhaps using filters, but you will not find a Local Folders folder on disk in the ImapMail subfolder to use. That may explain the content you moved there to vanish - I think any message synchronization / retrieval may just resync to what’s on the server, so unknown local content is removed.

The difference between an Archives.sbd folder containing files and single files would be that the folder is created when subfolders exist. More on that can be found in this question and on this page, but you can play with it by creating subfolders and copying messages in Local Folders and already have found out. :)

And even though the formats of IMAP and POP messages are different, I think they should both be visible in Local Folders when dragging/copying/filtering them.

In the end you have a point about caracterizing this though, and I still wonder if the Local Folders prefs setting not properly storing may have affected the outcome. Personally and now knowing all this, I would still copy the entire profile from another system first so everything is retained and should be visible, click the OKs, then re-add the existing account for IMAP if needed before removing the POP one, drag messages within Thunderbird, and remove the POP account as a last step. It may sound late in the day, but there is this and this support article describing that.

Does all this make sense?

The narrative has wondered but the path re: the archived emails (without detours) was as follows:

(1) Downloaded and installed Thunderbird on new computer. Used the IMAP settings as email account / server now IMAP = no archived emails shown - no Archive folder in Thunderbird at all. Again, all of the emails previously archived on the old computer were done when I was using the POP account / server settings.

(2) Used File Explorer to find archive files on HDD from old computer (via SATA to USB adapter). The "file sets" (no extension and .msf files, named by years) were in the Mail/pop.cox.net/Archives.sbd folder.

(3) Copied everything under the default profile folder on the HDD to under the new default profile folder created by the new install on the new computer using File Explorer (per the transfer profile suggestions in Thunderbird support).

(4) Still no Archive folder shown in Thunderbird and no archived emails.

(5) Changed the location of archived emails in Thunderbird from ******@cox.net to Local Folders. Archived a recent email to create the Archives folder under Local Folders in Thunderbird. This also created an Archives.sbd folder under the Local Folders folder on the new hard drive (as seen by File Explorer).

(6) Used "New Subfolder" function (right clicking the new Archives folder under Local Folders) repeatedly to create the "subfolders" 2007, 2008, etc. to 2016 in Thunderbird (again, not sure if required but then again, it may have been as it may have given Thunderbird the "map" to these "subfolders" (I know nothing of the inter-workings of Thunderbird or database programs, etc.)) This also created new, "empty" "file sets" with the 2007, 2008, etc. to 2016 names, under the new Local Folders/Archives.sbd folder, as seen in File Explorer.

(7) Closed Thunderbird. Used File Explorer to copy all of the 2007, 2008, etc. "full" "file sets" from the Mail/pop.cox.net/Archives.sbd folder to the Mail/Local Folders/Archives.sbd folder (copying over the new "empty" ones that were created by Thunderbird when I added the "New Subfolders").

(8) Opened on Thunderbird. There they were!