folders are stored in a hierarchy so all folders hang off a "parent" These parent folder are the ones with the ˃ and ˅ before them. In all probability the folder have moved somewhere off screen in the list of folders because it has moved up or down in the hierarchy.

Thanks, I understand about parent/child folders, and I've looked in all the parent folders, including the ones with multiple levels in the hierarchy, but the missing folder is just not there. Any other ideas? I appreciate the help!

One possibility, of course, is that I accidentally deleted the folder, but I can see the movement of the folders in my head -- the B folder floating over the A folder as if I were putting it inside as a subfolder -- but that didn't happen. It looks to me like Thunderbird doesn't have a failsafe for deleting folders -- is that correct? It doesn't prompt with an "are you sure?" dialog? And deleted folders don't go into the trash?

I've been using Mozilla programs for years, very happily, but this puzzle has me stumped!

deleted folders become a sub folder of the trash folder. Or at least mine do. Unless you hold shift. That bypasses the trash folder, both for deleting mail and folders.

Perhaps open the physical profile folder (Help menu > troubleshooting information > show button and search for a file with the name of the missing folder (folders in Thunderbird are stored as files in the operating system with the same name. So the "old mail" folder in Thunderbird will be a file in the operating system called "old mail".

My problem is similar, perhaps a manifestation of the same bug. I have started to use Box Sync for backup, but it has a file-size limit of 250 MB, and the mbox file for Inbox was well over that. To address this problem, I created an Inbox subfolder for each two years I've used Thunderbird, moved the corresponding messages into them, and compacted. This satisfied Box's requirement, but the 2016–2017 folder is empty! I cannot find messages for these years anywhere, including Trash. And no, I did not use the shift key at all; I didn't know about the option, described above, to bypass Trash. If I inadvertently deleted any messages, they should have gone to Trash.

I made no direct changes to the profile, using File Explorer only to see file sizes. All my moves were done by selecting and dragging in Thunderbird.

@pmbrown Given the nature of your last question a month ago, my first reaction is you have an anti virus problem. However you issue while it might be related is of little interest to the original poster on this thread and I suggest you post a new question and include the details of your mail provider, types of accounts (IMAP or POP) and what add-ons and anti virus you use. I have seen recent issues with kaspersky and ESET, McAfee has been a problem child for years and Nortons has some special problems all it's own the make the new account wizard not work.

@pmbrown Given the nature of your last question a month ago, my first reaction is you have an anti virus problem. However you issue while it might be related is of little interest to the original poster on this thread and I suggest you post a new question and include the details of your mail provider, types of accounts (IMAP or POP) and what add-ons and anti virus you use. I have seen recent issues with kaspersky and ESET, McAfee has been a problem child for years and Nortons has some special problems all it's own the make the new account wizard not work.

There is something wrong with this support forum. I am MSEL. However, I did not post anything at all to this Q&A thread. Yet a post in my user name has appeared, which is duplicated verbatim by Matt. I am going to try to report this to Mozilla.

Okay this is completely haywire. I just posted from my MSEL user account, and my post shows as originating from Lunaea.

Lunaea said

Okay this is completely haywire. I just posted from my MSEL user account, and my post shows as originating from Lunaea.

I had to log out and log back in to clear whatever was going on this morning.

I have already asked for help on resolving the issue.

MSEL here, not Lunaea or whomever else this post may show as originating from. My attempts to contact Mozilla went in circles, due to their bureaucratic firewall against contacting them directly. Mozilla has turned into an unresponsive hydra headed monster like Google. All contacts lead back to support forums, yet Mozilla does not have a support forum to report flaws to its own support forums. Hence, I have posted the problem in a Thunderbird support forum here

https://support.mozilla.org/en-US/questions/1211097

Lunaea said

I was moving an email from Inbox to (let's call it) FolderA, but accidentally selected FolderB somehow. When I tried to move my cursor (and the email) from B to A, FolderB disappeared. I thought I must have accidentally moved FolderB into FolderA, but it's just vanished. I've looked in all the other folders to see if FolderB is a subfolder there, but no luck. I tried searching for the message I accidentally put into FolderB, but nothing came up. I need that folder! Any suggestions? Thanks in advance! I have read the "help" pages all day and I still can't get the dang app to work. I did have it since it became available but it all of a sudden I can't find it.

pattiparker said

Lunaea said

I was moving an email from Inbox to (let's call it) FolderA, but accidentally selected FolderB somehow. When I tried to move my cursor (and the email) from B to A, FolderB disappeared. I thought I must have accidentally moved FolderB into FolderA, but it's just vanished. I've looked in all the other folders to see if FolderB is a subfolder there, but no luck. I tried searching for the message I accidentally put into FolderB, but nothing came up. I need that folder! Any suggestions? Thanks in advance! I have read the "help" pages all day and I still can't get the dang app to work. I did have it since it became available but it all of a sudden I can't find it.

Me too!!

Can you access what I have done so far remotely

and fix any problem area in Thunderbird?  PLEASE, I'm going crazy!!

Pattiparker, this thread is solved. It has nothing to do with you. Stick with the thread you started and answer the questions there by the person trying to help you.

I will just lock this thread. It is confusing enough with the wrong parties names against posts.