I think it's rather the mail file contents what's corrupted than a disk problem.

First of all create a backup of your Thunderbird profile folder. https://support.mozilla.org/en-US/kb/profiles-tb#w_backing-up-a-profile

Then try to rebuild the index file of the troubled folder. Right-click the folder - Properties - Repair Folder

Note: depending on the corruption this may erase messages from the affected folder which cannot be recovered anymore. In that case you'd need to restore them from a recent backup done prior to the 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 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

Also see http://kb.mozillazine.org/Keep_it_working_-_Thunderbird

Though helpful, the above information does not solve the issue. In this case it was absolutely the failing SSD (not anti-virus, etc..) It gave a lot of problems -- I'm seeking help for the Thunderbird portion here.

I have tried the "rebuild folder" option with no joy. It tells me the file size is 174Mb and message count is 0. Is there any way to extract information from that file.

I do have good backups from a while ago. However, because the corruption was slow at first, then more progressive as time went on, and since the last 3 weeks are most critical, those are the ones I'd like to salvage --- if possible.

Thank you for any help you can offer.

Any Ideas?

It tells me the file size is 174Mb and message count is 0.

Can you explain that in more detail? What did you do to get that information? What is 'it'? What file is 174 MB?

Click on the folder "Sent". Right click then select "Properties". In the small box that appears, just under the "Location" line, it says: Number of messages: 0 Size on disk: 174 MB

Is there any way to extract information from that file?

The problem is similar for the "Inbox", though it does give the correct number of messages.

Number of messages: 3147 Size on disk: 431 MB

The difference with "Inbox" is it shows the messages in the message window, but when they are selected, it does not read the info of the message -- just get a blank screen -- as if the email had not content.

Actually that's not totally true, because it does show content of the emails in the first 1/4 of the messages -- the old ones. I can also see content of messages in sub folders that were not accessed during the time the SSD was having problems. Those appear just fine.

The errors are weird, because, as it was explained to me, the SSD did not write everything correctly as it began to fail. Some files can be read by their parent programs, some, like these email files, cannot. It seems like in the read process that Thunderbird is not finding some key things it's looking for, so it just skips over those. I'm just wondering if there is a way to extract what is good info versus what is missing or garbage.

Thank you for any help you can offer.

I have tried the "rebuild folder" option with no joy.

What happened when you pressed 'Repair Folder'?

Is there any way to extract information from that file.

Mail files are text files. They can be opened with a text editor, e.g. Notepad++. Don't try the Windows Notepad. Check whether the mail still exists in the Sent file. Make sure Thunderbird is closed when you do that.

The difference with "Inbox" is it shows the messages in the message window, but when they are selected, it does not read the info of the message -- just get a blank screen -- as if the email had not content.

That sounds like the classic mail file corruption - see above. https://support.mozilla.org/en-US/questions/1128964#answer-892115

In this case it was absolutely the failing SSD (not anti-virus, etc..)

I'm not convinced about that.