So there's no other profile, and no other folders. That means your missing folders appear to be lost.

It is not clear to me why there is no backup when you did recover lost data previously by restoring a backup.

As said before, anti-virus software is the most likely cause having caused this mess. Therefore make sure to follow the suggestions given earlier. https://support.mozilla.org/en-US/questions/1152415#answer-948899

In addition, create backups of your profile folder on a regular basis. https://support.mozilla.org/kb/profiles-tb#w_backing-up-a-profile

OK. I agree that antivirus is responsible for the mess I'm left with and the antifirus is now set to 'not scan' email profiles, emails, etc and my ISP traffic. So goind back to where we started, I am still left with the original 'Deleted' folder, which is not recieving deleted emails, and the original 'Sent', 'Junk' and 'Drafts' folders are no longer there. Can anything be done to recreate these and bring the 'Deleted' folder back to life. The reason that you cannot find a 'Backup' is that I use 'KLS Mail Backup' to do this. It's a program that I've used on two previos email system without any problems whatever.

The email side is now solely IMAP

Then all your mail is on the IMAP server. The 'Local Folders' account is completely independent from the IMAP account.

the original 'Sent', 'Junk' and 'Drafts' folders are no longer there.

I don't see any reason why you'd need any of those underneath 'Local Folders' when you don't send or receive messages via 'Local Folders'.

Not sure Iagree with your latest response. My IMAP admin account, (on <daily.co.uk> website), is set to delete emails 48 hours after they have been picked up and this elimates the problem of having to remember to manually delete messages before the 'daily' mail box is full and won't accept further email inputs. You are correct in saying that my 'Sent' emails are available on the IMAP account at <daily.co.uk> as that folder is not set to empty automatically.

In relation to Thunderbird, the 'Deleted folder shows under 'Local Folders' but has stopped working and is empty. Consequently, if I accidently delete a file, it cannot be recovered. I need a'Drafts' folder because if I am generating an email on Thunderbird and stop half way through, that part finished email is never giong to be sent to my IMAP account,. This is also true for the 'Junk' folder, because if Thunderbird mistakes a file as junk when it is'nt then currently that email will simply disappear and I will never know that it arrived. In relation to the 'Sent' folder, if I'm working on an email that relates to an earlier email and want to check something in the earlier message, then I do not want to stop and log in to my IMAP to do it. Note: all these folders worked as expected for a while before the problems started.

In relation to my antivirus program, (Bitdefender) which is currently the suspected cause of the corrupted Thunderbird system, I had a look at the what thier email scanner did. I was surprised to discover that the email scanner only handles POP3 protocols. My assumption is that when the antivirus system scans incoming emails and emails stored in Thunderbird folders it finds something unexpected, and treats the folder and contents as an 'Infected item' and removes it. I have opened a support ticket with Bitdefender, outlining the problem and querying if the entries I have put in the 'White List' is sufficient to stop the problem The ticket has been acknowledge but 48 hours later i still await a response. I will copy you when I get a reply from them.

Update on Thunderbird problems.

Following suggestion that the Antivirus program was probably the cause of the problems arising in the email packet, I raised a support ticket with'Bitdefender' on 5/01/17. I decribed the problems that I was having with Thunderbird and asked if it was possible that the bitdefender email scanner was treating IMAP files and Folders as 'Infectide' items. On 7/01/17 I received a "we are investigating and will update you shortly" reply, ( I guess that's a "Yes". !. Having added 'Thunderbird' to the antivirus 'White List', there have been no further deletions of emails but I have discovered that when i send an email it is copied into the 'Inbox' Also, whilst looking around the email siftware earlier today I found an IMAP profile. Not sure when that appeared but screenshots are attached. Have decided to leave Thunderbird 'as is' for now and wait for the update from Bitdefender before doing anything else. Once Bitdefender declare the mail checker as 'safe' I'll install a clean version of Thunderbird and take it from there

Think earlier message today was sent via an incorrect route.So to update again latest results are as follows: Yesterday I noticed that when downloading emails, odd emails would 'disappear', presumably being sent to the non-existing 'Junk' folder. Clicking on the 'Inbox' had no effect. Today, the same thing happenned and again odd emails disappeared. I clicked on the 'Inbox', the screen flashed a couple of times and then all the missing Folders and thier contents reappeared. Everything that was missing is back and everything is working as it should. Am rather mystified. Then suggest reason for the disappeared date was that the Antivirus program was causing the problem, ( it does not support IMAP email), and a support ticket was raised with 'Bitdefender' That ticket is still open and only response so far is "We are looking for a solution to the problem". Having recovered from the surprise re-appearance of all the Thunderbird data I decided to have a look at the Antivirus status. I found that it had been turned off, (My system is on 24/7). and would not respond to being re-activated. I did a 'Re-boot' and the Antivirus reappeared and active again. Checked Thunderbird again after the reboot and was pleased to find that all the stuff that had disappeared is still there. Think the most likely answer to the surprise recovery, is that Bitdefender have downloaded something overnight which has recovered the situation , but await an uppdate from them.

Glad to hear you've got your stuff back. Make sure to create backups of your Thunderbird profile on a regular basis as suggested earlier in this topic.

Spoke too soon. Thunderbird worked as normal from 9am until around 6.30 pm. Then recieved an answer to the Bitdefender support ticket. They suggested I downloaded the latest version of Bitdefender and then turned all protection modules 'Off' and then bring them back on line one by one while keeping an eye on Thunderbird. Did that, and then opened Thunderbird. Thunderderbird has reverted back and everything apart fromm the 'Inbox' has gone again. So I guess the problem is now firmly with Bitdefender. From what happened this morning, I guess all the missing stuff is buried somewhere in the antivirus software. I've dropped the problem back in their lap and will keep you updated

Have finally resolved the problem. The latest version of Bitdefender anti-virus still only supports POP3 email protocals If one is using IMAP email protocol, ( as I am), then the initial download of Bitdefender will corrupt Thunderbird and all files and folders, apart from the 'Inbox' will disappear. I have not been able to discover where the folders go when they disappear as they do not appear in Thunderbirds Profiles. However, the missing stuff does continue to operate as having run my system for several weeks without them,, on recovery I found that everything that occured whilst the folders were 'Hidden' is accurately recorded. To fix the problem, When the folders disappear, open 'Bitdefender'and systematically turn each protection module 'Off'. While doing this, have Thundrbird open and on screen. At some point, (probablly when all items are de-activated), the Thundrbird window will flash and all the missing stuff re-appears. Now open 'Bitdefenders' 'White List' and enter, <C:\Users\User Name\AppData\Roaming| Thunderbird\>. Finally, turn all the Antivirus modules back on and Thunderbird should remain stable. The only down side to this is that incoming emails will not be scanned by the antivirus program, so be careful when opening strange emails. I think the POP3 scanner is what was causing the problem as it cannot handle IMAP stuff. Thanks for all you support whilst trying to resolve this problem.