I assume you are also seeing connection errors of some sort. What are they?

I’m not seeing any error messages. I see the folders in the subscribe list but they do not allow subscription. No message why.

open the error console (ctrl+Shift+J) clear it by clicking the trash icon. attempt to subscribe. What error appear?

What mail provider? I think there are three or four similar post this morning so some provider may have issues.

xxxxx

xxxxx

Ok, thanks. I cleared the error panel and unsuccessfully tried to subscribe folders. No new errors showed up. When I restarted thunderbird, these errors appeared:

[Exception... "Component returned failure code: 0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH) [nsIXPCComponents_Utils.readUTF8URI]" nsresult: "0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH)" location: "JS frame :: resource://gre/modules/L10nRegistry.jsm :: L10nRegistry.loadSync :: line 658" data: no] L10nRegistry.jsm:658:19 Successfully loaded OpenPGP library rnp.dll version 0.14+git20210121.7c8492b4.MZLA from C:\Program Files\Mozilla Thunderbird\rnp.dll RNPLib.jsm:95:15 Found 0 public keys and 0 secret keys (0 protected, 0 unprotected) RNPLib.jsm:291:15 [Exception... "Component returned failure code: 0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH) [nsIXPCComponents_Utils.readUTF8URI]" nsresult: "0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH)" location: "JS frame :: resource://gre/modules/L10nRegistry.jsm :: L10nRegistry.loadSync :: line 658" data: no] L10nRegistry.jsm:658:19 [Exception... "Component returned failure code: 0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH) [nsIXPCComponents_Utils.readUTF8URI]" nsresult: "0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH)" location: "JS frame :: resource://gre/modules/L10nRegistry.jsm :: L10nRegistry.loadSync :: line 658" data: no] L10nRegistry.jsm:658:19 [Exception... "Component returned failure code: 0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH) [nsIXPCComponents_Utils.readUTF8URI]" nsresult: "0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH)" location: "JS frame :: resource://gre/modules/L10nRegistry.jsm :: L10nRegistry.loadSync :: line 658" data: no] L10nRegistry.jsm:658:19 [Exception... "Component returned failure code: 0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH) [nsIXPCComponents_Utils.readUTF8URI]" nsresult: "0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH)" location: "JS frame :: resource://gre/modules/L10nRegistry.jsm :: L10nRegistry.loadSync :: line 658" data: no] L10nRegistry.jsm:658:19 getOrCreateFolderForURL: factory not registered for owl://peter%xxx.com@outlook.office365.com/Sent%20Items 2 FolderLookupService.jsm:76 getOrCreateFolderForURL: factory not registered for owl://peter%xxx.com@outlook.office365.com/Drafts 2 FolderLookupService.jsm:76 getOrCreateFolderForURL: factory not registered for owl://peter%xxx.com@outlook.office365.com/Archives 2 FolderLookupService.jsm:76 getOrCreateFolderForURL: factory not registered for owl://peter%xxx.com@outlook.office365.com/Templates 2 FolderLookupService.jsm:76 Trying to load C:\Program Files\Mozilla Thunderbird\libotr-5.dll OTRLib.jsm:51:11 Successfully loaded OTR library C:\Program Files\Mozilla Thunderbird\libotr-5.dll OTRLib.jsm:59:13 NS_ERROR_NOT_AVAILABLE: PreferDisplayName: undefined - not a boolean 3 AddrBookCard.jsm:197

​

Also, my account is through GoDaddy.com. (BTW, the GoDaddy rep said that there was no error on their side and that Thunderbird is no longer supported by Mozilla and I should use Mailbird. (!))

Wow! Another GoDaddy customer. I feel your pain. I have had nothing but problems since being forced off WorkSpace and onto OWA two weeks ago.

I have several mail accounts and my folders just seem to randomly come and go. I have GB of e-mail, so when they come back the computer spends all day downloading e-mail, as Thunderbird deletes everything.

One thing that I am not sure if it helps or not. Go to Account Settings. Then Server Settings. Then Advanced... There is an option Show Only Subscribed Folders. Make sure it is not checked. Click OK.

I found that I had to then quit Thunderbird. When I started again, the folders appeared. Of course, it also meant ALL those e-mails had to be downloaded again.

Trying to use subscribe just did not seem to work. I can go to the Subscribe dialog. All the folders are there. I can check them and Subscribe, but they do not show up.

If I go to Account Settings -> Synchronization and Storage and under Message Synchronization choose Advanced, the folders are not there. UNLESS by some magic they got downloaded and then they show up. I am hoping the magic is what I suggested above and that it sticks this time.

My business is suffering at this point- 50% dealing with customers 50% trying to get usable e-mail for the last two weeks.

My next step was to exit Thunderbird and copy

C:\Users\Me\AppData\Roaming\Thunderbird\Profiles\ ...

to another folder. Assuming all the e-mail downloaded, now at least it is backup up.

That is not the end of my problems- I still cannot send mail from Thunderbird.

Also if any experts are reading this-

My profile is filling up with what look like artifacts when my folders get lost and reappear. For example, I now have Sent-Items and Sent-Items-1 (with and without the msf suffix). The former are empty and the latter seems to have been created when I finally got my folders to show up again and everything started downloading a second time.

Is this going to be a problem? Should I just delete the profile and try again fresh?

Wow, James! the first suggestion did the trick! All my folders showed up, when the subscription restriction was removed in advanced settings, AND all the emails were there. That does still leave the question of why can't they be subscribed (and what is 'subscribed' anyway). Also, why did it suddenly happen. In any case, I'm a happy camper for the time being. I'd love to blame godaddy but will hold off for the time being. Thanks again!

PS: Despite my folders being back, I still get that long string of errors on start-up...

I was a little bit chastened yesterday when following my own suggestions, all my folders disappeared again.

The reproducible part is that I start Thunderbird. I have not made it my default e-mail client. I am presented with the System Integration dialog when it starts. My AppData folder has all the mail and the msf files. The folders are being displayed in the GUI. Then I select Skip Integration, and the files are all deleted and the folders disappear from the GUI. I have the option set to check for mail on start-up. So I assume that check finds no folders and proceeds to create havoc.

As a suggestion to those bright enough to contribute code to Thunderbird, it would help to have more feedback on what Thunderbird thinks the Subscribe, Advanced Account Settings, and Message Synchronizing are actually set to.

I am avoiding Subscribe. If I go to that dialog, nothing is ever set. I do not know if folders are or are not subscribed. With this folder disappearing problem, unsubscribing deletes all my mail in AppData and re-subscribing usually does not even remake the msf files. I would like better feedback on what Thunderbird actually thinks I have subscribed to before making changes.

When my mail disappeared yesterday, I had Keep messages in all folders for this account on this computer checked. As part of debugging, I hit Advanced and found almost every folder was unchecked. I hadn't changed anything there! It would be nice to have some feedback that Thunderbird was not keeping all messages. No idea why that setting changed nor any idea what happens if all the Advanced boxes are unchecked but the Keep messages checkbox is checked.

Still a little concerned folders are going to go away again. But at least there seems to be ways to get it reloaded.

I totally suggest everyone make a copy of their profile folder!

As an aside, I am pretty unhappy with GoDaddy, but only for dropping WorkSpace. I saw a whole bunch of comments in 2016 about Microsoft introducing a bug that cause this same problem. It started affecting only some accounts and spread as they updated their servers. That is consistent with what I saw, as first it was just one of my e-mail accounts, but the problem has spread to all of them.

Hello jtswanson and chicagostories. This solved my problem

''Go to Account Settings. Then Server Settings. Then Advanced... There is an option Show Only Subscribed Folders. Make sure it is not checked. Click OK.

(Now all the messages in the disappeared folders are re-loading, but I can deal with that as long as it doesn't happen every time I open Thunderbird.