First of all create a full backup of your Thunderbird profile folder. This article may help. http://kb.mozillazine.org/Thunderbird_:_FAQs_:_Backing_Up_and_Restoring

You need to understand what compacting is and why it's needed. http://kb.mozillazine.org/Compacting_folders

It isn't normal that messages disappear after compacting. This can be caused by mail folder corruption. Corruption is often caused by anti-virus software messing with Thunderbird mail files. It is therefore recommended to create an exception for the Thunderbird profile folder, so that the anti-virus real-time scanner won't attempt to scan the profile with your mail. For more information on the profile location see http://kb.mozillazine.org/Profile_folder_-_Thunderbird

Inbox is most susceptible to corruption. It is therefore best practice not to accumulate messages in Inbox. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

Briefly examining the beginning and end of this file with a plain text editor suggests that this file may contain the missing contents of my Inbox.

That sounds like messages still exist.

If I exit and restart TBird will this file be deleted?

The file will not be deleted. But depending on the status of the corruption it's contents can be altered, including deleting stuff which is in there now. But since you created a backup you can always restore the file if needed.

Will the contents of the Inbox become available?

Try to rebuild the index file for Inbox. Right-click Inbox - Properties - Repair Folder

Any better? In worst case the contents of Inbox will get deleted. Then we'll have to look at the restoring a backup route.

christ1, Following your advice and rebuilding the index appears to have restored my Inbox. Thanks very much!

That leads to another question, which might be addressed under a different topic. Although I don't see anything obviously missing from the new Inbox, it seems likely that some messages would be missing or damaged. Can I access the backup copy of my Inbox so I will be able to compare the two versions side by side? (Perhaps I could rename the backup version and copy it to the directory with the mail folders?) Is there some kind of program that would allow me to compare the two versions if my Inbox and produce a list of messages that are different? Or perhaps I could copy the messages from the backup copy to my current Inbox and there might be some kind of program that would eliminate the duplicate messages?

I will follow your other advice and change the way I use TBird so this will not be so likely to happen again.

Many, many thanks! Lloyd

I'd extract the profile backup to a temporary location. you can then import the Inbox folder to where ever you like using this add-on. https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

I'd rather import to the 'Local Folders' account. You could then compare the number of messages per month between the actual Inbox folder and the imported one. That can easily be done by highlighting all messages received in a month. That sounds less work to me than getting rid of the duplicates later. If you want to go that route, look for an add-on which finds duplicate messages on AMO. https://addons.mozilla.org/en-US/thunderbird/

The problem with just happened again today, very much like when it happened the first time. I had booted the system and clicked to get new mail, read the first message, clicked to delete it, and TBird asked me if I want to compact folders. When compacting was complete the inbox was empty. I made a copy of the mail folders, rebooted the system, and rebuilt the index for the Inbox, and the Inbox appears to be restored.

There must be a serious problem with TBird on my system. How could a catastrophic error like this occur and have it produce no error message??? Is there some way to find out why this is happening?

I have not yet moved to contents of my Inbox to another folder or excluded the Inbox from virus scans, but I haven't run any virus scans since the previous time when the contents of the Inbox disappeared. Other than this TBird problem, the system seems to be completely stable and reliable. (I have been using a program called Quick Startup to change the order in which some of the programs are run when Windows boots in an attempt to make the icons visible in the notification area on the task bar, but I do not see how that could cause this problem.)

I need to find out what is wrong so I can be sure it doesn't happen again.

Thanks for your help! Lloyd

I have not yet moved to contents of my Inbox to another folder or excluded the Inbox from virus scans

Then I'd suggest you do this ASAP. Not sure what you're waiting for.

but I haven't run any virus scans since the previous time when the contents of the Inbox disappeared.

I'm not sure what you're trying to say here. Anti-virus scans your Inbox file every time you receive a message or when you delete one.

There must be a serious problem with TBird on my system.

There is no point speculating when you don't follow instructions.

There seems to be some kind of serious defect in Thunderbird, and at least on my system it looks like it is reproducible. Is anyone out here interested?

I'm not sure what you're trying to say here. Anti-virus scans your Inbox file every time you receive a message or when you delete one.

Doesn't preventing the antivirus from scanning Thunderbird defeat the purpose of running an antivirus program, since most viruses enter the system through infected E-mail?

First of all, not everything is a virus. http://lifehacker.com/5560443/whats-the-difference-between-viruses-trojans-worms-and-other-malware

Wrt your question see http://thundercloud.net/infoave/tutorials/email-scanning/index.htm

and http://kb.mozillazine.org/Thunderbird_:_FAQs_:_Anti-virus_Software

https://bugzilla.mozilla.org/show_bug.cgi?id=1236361

Along this same line, I was individually "compacting" a folder I use for archiving messages and it did the same thing. It deleted ALL the messages! I've created test folders and transferred files into them to test this again, and sure enough: Poof! All gone.

I'm afraid to bulk compact for fear of losing everything. I'll create a backup Local Folders directory, but this should not be happening.

Any constructive thoughts appreciated.

Fred, You could post your problem as a question on this forum, or your could do what I did and go to: https://bugzilla.mozilla.org/ You begin by clicking to file a bug report. It leads you through the process, and the first thing it does is show reports of similar bugs. You should look at those bugs and see if any of them are duplicates of your problem. If so, then you add yourself to the list of people who have the same problem. If none of them describe your exact situation, then you should report a new bug.

You can learn a lot from reading the reports of similar bugs. You will see what other people have done to work around or to resolve the problem.

Lloyd,

That would be another place to go look for clues. Thanks.

Even though it wasn't my Inbox, I thought the problem was similar enough to warrant a post here. I'll head over to the other forum later tonight.

Fred

Fred_B,

I'll head over to the other forum later tonight.

Please re-read what Lloyd wrote:

You could post your problem as a question on this forum

In other words, start your own thread for your problem. Bugzilla is not a support forum.

christ1,

Thanks. I'll post it as a new thread later today after I get back over to the shop and check that particular computer (XP). The one here at the house is not having that problem (Win7).

Also, I checked and in his original message Lloyd mentions a different version to Thunderbird than mine here at the house. He mentions 42.0 and mine is 38.7.1. (? And yes, I hit the update button. ) I'll see what version is on the office machine.

My version number was incorrect. I think I got that number from Firefox instead of Thunderbird.

I had to chuckle as I thought I was getting gypped only getting 38.7.1. (smile)

I posted over here: https://support.mozilla.org/en-US/questions/1115897

The office machine did it again...and then it didn't. I'm confused. I've just taken to backing up newer folders should it act up again.