there is no mail in any f the folder you mention other than the zip-urb folder. (the file zip-urb being the mail.

The file Zip-Urb has zero bytes. Does it mean all the mail is lost?

The existence of an MSF file would indicate that you have perhaps set the account up to not have messages stored offline, so their is only sufficient information downloaded from the server to populate the user interface with mail lists.

Files with not extension.... MBOX formetted mail files. Same as MAc Mail used years ago. Not now.

MSF files. INdex or database files. Depending on who you ask and really to some extennt the account settings. used to populate mail lists and hold pointers to the mail in the mail file or hold the reference used by the server for IMAP mail.

sdb folders. Signify that the folder within Thunderbird has a sub folder. in the file system if holds the MSF files and MBOX files for the folder.

If your account is IMAP, the proviso the above comments are predicated on. Have you got an anti virus or firewall program that might be blocking the new version68 from actually accessing the mail server to display the mail? This is very common on windows and becoming more common on apple where such programs are becoming popular.

This is not the live email part of my account and is nothing to do with IMAP. This is my email archive, locally stored on disk.

Up until last week, my hierarchy of archived email was showing fine. Nothing changed in the meantime i.e. no new anti-virus, no system changes.

Although I did not mention it, I have another folder alongside Zip-Urb, and that has subfolders and everything is fine there.

I have now realised that for every bottom level folder, there should be

 myname
 myname.msf

But I only have

 myname.msf

So something has wiped out every single

 myname

but left everything else

That explains why I do not see any email but I just have no clue how this could have happened.

paulbeardsley5 said

That explains why I do not see any email but I just have no clue how this could have happened.

Unfortunately, neither do I.

OK I guess that's a first then, if you did not see it before.

Potentially it's nothing to do with Thunderbird. I keep my local archive in an encrypted disk image. But I cannot see how that would wipe out some files and not others.

Thank you for your help in any case, even if it turned out to be a mystery.

In case someone else has this problem and looks at this thread later -

I went through my backups and found when the problem occurred. I was changing my folder organisation and I added a new high-level folder H and moved some existing folders A B C underneath it. (I did this using the Thunderbird interface, not by moving any folders directly on disk).

What I see when I look at my Thunderbird archive using Finder is that A B C still have some files in their original position i.e. not under the new high-level folder H. But there are no actual message files, only Thunderbird's meta folders/files - .sbd and .msf.

And there are also some A B C folders in the new position i.e. under the new high-level folder H. But again there are no actual message files, only Thunderbird's meta folders/files - .sbd and .msf.

My best guess (I cannot say it with certainty) is that when I moved the folders A B C, Thunderbird messed up the move and left meta folders/files in both the old and new positions, but deleted all the <message> files underneath A B C.

I'll report this as a bug if that seems worth doing. But I would not know how to replicate it - I have moved folders before without this happening.