You appear to be assuming it's Thunderbird who marked those messages as junk, which I have a hard time believing is what happened. The junk filter is applied to incoming messages, not to messages already on the server. And if it was Thunderbird who did it, it would not have marked as junk messages for which the sender is in your address book, according to your settings. Did those messages have the banner saying "Thunderbird thinks this message is junk mail" or were they just moved to the Junk folder without being really marked as junk?

My e-mail-server was moved to another provider.

It's unclear to me what does this mean… How was your mail moved from the old provider to the new one?

Thank you. Yes, I am sure Thunderbird marked these emails as Junk. My address book is empty, so the related Thunderbird setting does not help with anything. So I have turned that setting off.

The server admin set up a process of moving all messages to the new provider. I was not privy to that process, but it took a couple of hours, and I was required to set up a new IMAP account. I did this on two machines, and everything was fine (a laptop with Thunderbird and a phone with K9). The messages all retained their state (read or unread, some flagged, etc.).

After a few days, I took the opportunity to start using a virgin Thunderbird installation on a desktop computer where I had not used Thunderbird before. That Thundebird installation had to download all messages anew, and while doing so, filtered 7,299 of them erroneously as Junk into the folder I had specified in the settings.

This even includes messages I have sent myself.

How do I get them back?

Someone else may know better, but I don't think you'll be able to get them back other than by moving them yourself manually or using message filters.

You talk about the messages being originally in folders, but Thunderbird would only have marked as junk messages that were in Inbox, not in those other folders. What you described sounds very strange to me. Something doesn't compute here…

I checked, and it seems that the address book option *is* activated. So that wasn't it.

re : I set up a new IMAP account in Thunderbird 128.7.0esr.

An Imap account means you have to use the server default folders. Usually, most servers do not use the word 'Junk', they usually use a folder called 'Spam'. It's important to know what is the correct name for the server default spam/junk folder.

How to tell what folder is the server default spam/junk folder: Logon to your webmail account via a browser, it will list the default folders and any other folders you have created. If you select an email and say it is junk where does the server put it ? If it puts it into a folder called 'Spam' then that is the name of the folder you must use in the imap account in Thunderbird. So lets assume it is called 'Spam' Please provide an image of the webmail list of folders so we can check and understand what your server uses.

In Thunderbird In the Folder PAne you should see the name of imap account and it should also have a 'Spam' folder.

It would also be very helpful if you posted an image showing what you see in the Folder PAne. You should be seeing exactly the same as the webmail account.

Assuming it is Spam in webmail and Spam shown in imap..... You need to make sure that mail account junk settings are set up correctly.

• Account Settings
• Select 'Junk Settings' for the imap account.
• Select checkbox 'Enable adaptive junk mail controls for this account'
• Select all the address books you want to act as a whitelist now or in the future.

• Advise you do not select 'Trust junk mail headers set by' unless you really want that option.

Destination and Retention

• Select 'Move new junk messages to'
• Select 'Other' and choose 'Spam on mail account address'
• Advise you do not select : 'Auto delete junk...'

Then Exit Thunderbird and wait a short while for background processes to write to files. Start Thunderbird.

• How to tell what put emails in Junk/Spam:

In 'Spam/Junk' folder - Make sure the 'Spam' column header is enabled - it will use a flame shaped icon. If the flame icon is grey then the server put the email in the Spam folder If the flame is red/orange then Thunderbird put the email in the Spam folder - please note if Account Settings instructions are to trust junk mail headers then thunderbird will move the email to Spam/Junk - hence why I advised you do not set that option at this point.

Is the flame icon grey or coloured ?