Sorry for the late reply. Please confirm if I've understood the following correctly:

1. There is no nested Inbox folder in webmail. There is only one INBOX (the server's native/system Inbox folder) and it contains the messages (and subfolders, if any) that you expect it to.
2. The server's native/system Archive folder and all its contents as seen via webmail is what Thunderbird shows as the nested Inbox folder.

Also, please confirm if in webmail, the other server native/system folders (e.g Sent, Archive, Drafts, Spam/Junk/Bulk), Deleted/Bin) are subfolders of the native INBOX folder or NOT. This will explain whether that persistent personal namespace "INBOX" should be there or not as it affects the folder tree shown in Thunderbird's Folder Pane.

Thank you for hanging in there on this. I'll out gone next week so I may not respond for a while. In roundcube there is no nested inbox folder under Inbox. But otherwise even the roundcube layout isn't right, it goes like this:

Inbox --folders A, B, C Drafts Sent Junk Trash Archive folders D, E, F (not under Archive, they appear to be first level)

In thunderbird Inbox (multiple email account inboxes contained) Drafts Templates Sent (multiple contained) Archives (multiple contained) Junk Trash Outbox troublesome@domain.com --folders D, E, F (one of those folders is INBOX which contains A, B, C) straightforwardemailaccount@gmail.com

Hopefully this makes it clear.

Hmm I wonder why that posting (edited posting just a minute ago) needs a moderator to approve it? Are all posts here like that, and I just didn't notice the message?

It seems you're using the Unified Folders view in Thunderbird. Disable that view and enable the All folders view only via View > Folders > All. As a result, each distinct account in Thunderbird will be listed just once, with a folder tree below the account name showing all of the account's (subscribed) folders. It's the perfect view for troubleshooting what's going on in your case. You should now see the same folder heirarchy as the one seen via webmail. You can post screenshots (a picture is worth a thousand words) of the folder tree as it appears in Thunderbird vs webmail as we progress. That is more convenient than trying to describe what you see in words.

Some posts will trigger moderation if they contain texts that resemble links. This is normal behaviour by the forum software and is part of the spam/scam fighting strategies.

I don't think screenshot are practical here - the user has hundreds of folders. Minus unified folders, the relevant account is like this in thunderbird under troublesome@domain.com

Inbox --Drafts --Templates --Sent (multiple contained) --Archives (multiple contained) --Junk --Trash --folder D --folder E --folder F ... --INBOX

 --folder A
 --folder B
 --folder C

Webmail

Inbox --folder A --folder B --folder C Drafts Sent Junk Trash Archive folder D folder E folder F (not under Archive, they peer first level to Archive etc)

IOW even the webmail part seems confused. I think if you could tell me how to fix the webmail side, it might possibly help with the thunderbird side, or at least should be done first. To that end I wanted to use roundcube to create a new folder and see where it lands. I added a folder with no parent and it's presented at the top level as you'd expect. But while looking at the folder management view in roundcube I noticed that the folders that are shown in webmail at the top, A B C, are nested in a folder called "imer". Not sure what that is, I don't think the user created it, and I'm wondering if I should move all of those contained folders ABC outside of "imer"?

I don't think screenshot are practical here - the user has hundreds of folders.

Not a screenshot of all folders in the tree, obviously, just the top-level ones that can fit in a shot.

Minus unified folders, the relevant account is like this in thunderbird under troublesome@domain.com Inbox --Drafts --Templates --Sent (multiple contained) --Archives (multiple contained) --Junk --Trash --folder D --folder E --folder F ... --INBOX --folder A --folder B --folder C

If I'm reading the above correctly, ALL system folders are subfolders of the Inbox folder, as well as the extra INBOX folder. Is that so? Let's see what happens when you clear the IMAP server directory and Personal namespace fields in Tbird's advanced server settings. For the former, delete the entry to leave it blank while for the latter, uncheck the option labelled "Allow server to override these namespaces" then change the entry to an empty string, that is two doublequotes with nothing between them, like so (see attached image):

""

Restart Thunderbird and report back what has changed. Also confirm the empty string in Personal namespace remains after the restart since we're not letting the server override this.

Webmail Inbox --folder A --folder B --folder C Drafts Sent Junk Trash Archive folder D folder E folder F (not under Archive, they peer first level to Archive etc) IOW even the webmail part seems confused. I think if you could tell me how to fix the webmail side, it might possibly help with the thunderbird side, or at least should be done first. To that end I wanted to use roundcube to create a new folder and see where it lands. I added a folder with no parent and it's presented at the top level as you'd expect. But while looking at the folder management view in roundcube I noticed that the folders that are shown in webmail at the top, A B C, are nested in a folder called "imer". Not sure what that is, I don't think the user created it, and I'm wondering if I should move all of those contained folders ABC outside of "imer"?

I have no idea what the "imer" folder is too and web searches aren't turning up any meaningful matches either. In the folder management view, it should now be clear which folders are system folders and which ones are just regular user-added folder. You can tell by looking at the toggle switch next to each folder. The switches next to the system folders are disabled/inactive/greyed-out, meaning you cannot unsubscribe from them. The regular non-system folders can, on the other hand, be toggled to off. You can go ahead and move the A B C folders to a preferred parent folder and get rid of the "imer" folder if it is deletable. If it's a system folder, it won't let you delete it. In your depiction of the webmail view above, you've presented folders A B C as subfolders of the Inbox. In my Roundcube folder management view, I cannot use the Inbox as the parent folder for any new folders I've added. Inbox is simply not listed as an option for parent. Is that not the case on your end?

Thanks again Stans for your persistence and expertise. It is all interesting and you're exposing me to new things as we go along. In Advanced I made sure IMAP server directory was still blank, cleared the values in Personal Namespace and unchecked "allow server to override these namespaces", then closed and restarted tbird. No changes to the folder structure, and Personal Namespace is still empty and "allow server to override these namespaces" is still unchecked. I confirm that in roundcube the folders A B C are hived under the top level Inbox. Now that you mention it, that does seem peculiar, and the D E F folders that are seemingly top level folders (not under any system folder) seem more natural...because Inbox implies a received email, and the folders A B C contain both sent and received emails. Imer is not a system folder, it can be disabled. More on Imer: [1] The Imer folder is presented in tbird but it contains no folders; it does contain 10 or so emails, lo and behold to a company called Imer. [2] In roundcube, using the Mail view, the Imer folder contains same emails, and no folders. [3] In roundcube, using the Manage Folders view, the Imer folder contains the A B C folders (which are presented in thunderbird under the italicized INBOX entry). How odd is that? Since it's clear that the Imer is a user created folder for a company and shouldn't be hosting a heap of folders for other unrelated companies, it should make sense to move those folders out of Imer in roundcube. But I'm not sure how to do that. ALL of the user created folders have INBOX as the parent folder. And when I create a new folder in roundcube, selecting "-" as the parent folder, the Parent folder is set to INBOX when I check the folder's properties. The parent folder "-" is also the default value if I have just opened folder management and create a new folder. I'm not going to try to adjust any of this until I (hopefully) hear back from you re what might be the best path forward. I don't see a bulk update feature for folder properties...it's going to be a drag to adjust all of these folders by hand, but so be it. Note I'm sure the user has created these folder in both thunderbird and roundcube, depending on the time period.

In Advanced I made sure IMAP server directory was still blank, cleared the values in Personal Namespace and unchecked "allow server to override these namespaces", then closed and restarted tbird. No changes to the folder structure, and Personal Namespace is still empty and "allow server to override these namespaces" is still unchecked.

Re-enable the "allow server to override these namespaces" and restart Thunderbird then confirm whether the server has repopulated the Personal Namespace field with the Inbox or any other value. This is the desired outcome, even though you may not see any changes in the folder tree displayed by Thunderbird, it affects how user-created folders (aka mailboxes) are handled by the IMAP server. By all means, we want Thunderbird to use the correct personal namespace for this user as declared by the server.

I confirm that in roundcube the folders A B C are hived under the top level Inbox. Now that you mention it, that does seem peculiar, and the D E F folders that are seemingly top level folders (not under any system folder) seem more natural...because Inbox implies a received email, and the folders A B C contain both sent and received emails.

It does seem peculiar, but this is exactly how some IMAP servers are configured. It can be a cause for confusion for users when a client displays other folders as children of the Inbox. To add to the confusion, some webmail configurations don't show that same folder heirarchy, instead, they display these sub-folders as if they are of the same level (sibling) as the inbox, when in fact, behind the scenes, they are children of the Inbox!

Imer is not a system folder, it can be disabled. More on Imer: [1] The Imer folder is presented in tbird but it contains no folders; it does contain 10 or so emails, lo and behold to a company called Imer. [2] In roundcube, using the Mail view, the Imer folder contains same emails, and no folders. [3] In roundcube, using the Manage Folders view, the Imer folder contains the A B C folders (which are presented in thunderbird under the italicized INBOX entry). How odd is that? Since it's clear that the Imer is a user created folder for a company and shouldn't be hosting a heap of folders for other unrelated companies, it should make sense to move those folders out of Imer in roundcube. But I'm not sure how to do that.

Let's refresh Thunderbird's subscribed folders for this account and see if anything changes. Right-click the account in the Folder Pane, select Subscribe. In the list of discovered folders, select ALL folders. You can do this by clicking the first folder, scroll to the last folder, hold down the Shift key on your keyboard then click the last folder. This will select ALL of them. Click the Unsubscribe button then Refresh (this will uncheck the checkboxes next to each folder, but it's normal for some folders to remain checked, especially system folders that cannot be unsubscribed from). Select all of them again and click the Subscribe button. Refresh one last time just to confirm they are all checked then click OK and restart Thunderbird. Check if anything changes in Thunderbird's folder tree.

And when I create a new folder in roundcube, selecting "-" as the parent folder, the Parent folder is set to INBOX when I check the folder's properties. The parent folder "-" is also the default value if I have just opened folder management and create a new folder.

This confirms that Inbox is the correct personal namespace that Thunderbird should be using as set/overriden by the server and it's the parent folder for user-created folders (mailboxes) even though it may (confusingly) not appear so in the Mail view of webview or even in Thunderbird's folder tree. See my first paragraph above.

Let's perform a test as follows:

1. In Thunderbird, right-click the account and select New Folder. Give it a suitable name, say 00Test.
2. Check that folder in webmail mail view and note how it's displayed in the folder tree. Is it displayed as a child of the system Inbox or as a sibling (same level)?
3. In webmail Folder Management view, check the properties of the folder and note if it has Inbox as its parent.

This will confirm how the webmail presentation has been configured on the server vs how the account heirarchy appears in Thunderbird.

I'm not going to try to adjust any of this until I (hopefully) hear back from you re what might be the best path forward. I don't see a bulk update feature for folder properties...it's going to be a drag to adjust all of these folders by hand, but so be it. Note I'm sure the user has created these folder in both thunderbird and roundcube, depending on the time period.

Let's see what the outcome of the actions above is first. Has it affected Thunderbird's display? Is the extra INBOX folder still present in Thunderbird even after refreshing its folder subscriptions?

I confirm that "INBOX." is recreated as the value for Person Namespace with "allow server to override these namespaces" turned on and after a restart. And "INBOX" is still present in Thunderbird after refreshing subscriptions. Not sure if it happens every time, but when I select all folders and unsubscribe, eventually the boxes are unchecked, but if I then refresh, they're all checked again?

The 00Test folder experiment shows [1] thunderbird shows 00Test as a peer of system Inbox [2] webmail mail view presents as a peer of system Inbox [3] webmail folder management view also presents as a peer of Inbox, and the parent folder property has INBOX

Not sure if it happens every time, but when I select all folders and unsubscribe, eventually the boxes are unchecked, but if I then refresh, they're all checked again?

It does on my end too. Try that again, but this time round, Unsubscribe then click OK once ALL the checkboxes have been unchecked. This will close the dialog. Reopen the dialog and check if the unchecked boxes remain unchecked. They do on my end. Click OK then Restart Thunderbird and see what happends to the folder tree. Open the dialog once more, Select all and Subscribe, then click OK and restart Thunderbird. The folders should all be back in the folder tree. IF the extra INBOX folder is still present in Thunderbird (and still doesn't exist in webmail), try renaming it to something else and see what happens. Does it let you rename it or not, and if it does, does it appear in webmail with the new name?

I've unsubscribed and resubscribed to all of the folders. No changes to the layout as presented in thunderbird. Both parts took multiple passes before the folders were gone, and then back. I'm making these mods on my own instance of thunderbird, not that of the end user. I found that my changes were visible to the end user, which I had not anticipated. Does this mean the config changes are stored on a server somewhere, and were relayed to the other instance? I can't make the test with INBOX renaming until after business hours. Thanks again.

Lost a more detailed posting here, server error. in tbird renamed INBOX as INBOX test close and reopen tbird, now see INBOX and INBOX test roundcube shows only INBOX test in tbird renamed INBOX test as INBOX closed tbird reopen and have just INBOX again. When tbird showed system Inbox, INBOX and INBOX test, all three had different folders inside.

I've unsubscribed and resubscribed to all of the folders. No changes to the layout as presented in thunderbird. Both parts took multiple passes before the folders were gone, and then

It takes a while to subscribe/unsubscribe when there are lots of folders to handle. You just need to wait until all folders have been processed and their subscription status in the dialog has changed.

I'm making these mods on my own instance of thunderbird, not that of the end user. I found that my changes were visible to the end user, which I had not anticipated. Does this mean the config changes are stored on a server somewhere, and were relayed to the other instance?

No, Thunderbird doesn't store its settings on a remote server. Settings are stored locally on your computer on a per-profile basis, that is, each Thunderbird profile has its own set of configurations.

When using IMAP, the changes that are made to the mail folders and messages are synchronized across devices. For example, renaming, deleting or creating new folders. IMAP gives you a "mirror view" of the account as it exists on the server. Actions you take on the account's contents in Thunderbird are replicated on the server as any other client that accessing that account via IMAP, like you saw with the 00Test folder, which is why I find it odd that Thunderbird is displaying an INBOX folder that isn't seen in webmail, even after renaming it?

Lost a more detailed posting here, server error.

That happens sometimes. I've learnt to write long responses on a separate program, preferably a plain text editor to avoid losing it when a glitch occurs during posting. I use the Sticky Notes app for this, or copy everything to the clipboard just before posting. I've also enabled clipboard history so I can re-paste stuff when needed.

in tbird renamed INBOX as INBOX test close and reopen tbird, now see INBOX and INBOX test roundcube shows only INBOX test in tbird renamed INBOX test as INBOX closed tbird reopen and have just INBOX again. When tbird showed system Inbox, INBOX and INBOX test, all three had different folders inside.

I need to see what you see, and text descriptions are just not cutting it for me. I need to see what these three inboxes look like in Thunderbird. At some point you mentioned one of them is italicised. That doesn't sound like a user-created folder. Is it the one at the top of the tree, under which all the other folders including the extra ones are nested like you had depicted in an earlier comparison of the webmail vs Thunderbird? Let's see screenshots of the differences that matter.

The end user wants this fixed but doesn't think I should be taking much more time on it. I probably need to either give up on fixing this or cut to the chase if I can.

Manually changing the parent folder of the folder that are embedded under italics INBOX (in thunderbird) aka Imer (if roundcube) does seem to deal with the mixup. Do you know if there is a way to modify the parent folder for multiple folders in roundcube, or thunderbird? The closest I can figure it selecting multiple entries in thunderbird and moving them to the system inbox folder (or the parent email account). The issue with that is it's hit and miss how many folders make the move successfully and I worry that a folder and it's content will be lost. For example I just moved folders A B C and only A C moved, B is still in the original location.

Another perspective. In thunderbird this is the location of the accounts under non system INBOX (italics) imap://mazzz%40mozzz.com@s2.supportedns.com/INBOX/INBOX/Azzzz%20Plazzz

here is the location for a test account I just created and is in the appropriate spot in the hive imap://mazzz%40mazzz%40mozzz.com@s2.supportedns.com/INBOX/aaa%20test%20new%20folder

Not sure if that's helpful.

Do you know if there is a way to modify the parent folder for multiple folders in roundcube, or thunderbird? The closest I can figure it selecting multiple entries in thunderbird and moving them to the system inbox folder (or the parent email account). The issue with that is it's hit and miss how many folders make the move successfully and I worry that a folder and it's content will be lost. For example I just moved folders A B C and only A C moved, B is still in the original location.

No, I don't. Folder management via webmail or IMAP is very limited, as you've found out. I wouldn't do that via Thunderbird. According to Roundcube's documentation here https://docs.roundcube.net/doc/help/0.9/en_US/settings/folders.html you can drag and drop folders to the desired parent folder in the folder management view. It works gracefully this way, compared to doing it in Thunderbird, even though it doesn't let you drag multiple folders at once. I wouldn't recommend doing this in Thunderbird, no matter how tempting it is. Even if it takes hours to move them one by one to the desired heirarchy, that's what I would do via webmail.

Yes, it makes sense to perform the moves in the webmail ui. Thank you Stans! You've been amazingly helpful.

Note that if filters were being used either in webmail or Tbird to move messages into these folders, the filters may need to be reconfigured to point to the new folder paths after they've been moved.

Noted

Performed the folder moves last night. It appears to have been a success. Some parts were odd, for example when I renamed the Imer folder, so move it in the hierarchy of folders so that the manual changes require less scrolling to nav back to the next entry, the next in line folder because the host of the mass of folders that were under INBOX/INBOX. There was also a message from roundcube at some point stating that the IMAP server had encountered a serious problem and may have been corrupted. But it doesn't appear that it did actually corrupt. Thank you for your help with this.