"Spam" is not a Thunderbird word. If you do really have a folder named "Spam" then something outside Thunderbird is putting messages into it. This is usually your mail provider's spam detector, or it may be your own security software.

If you meant "Junk" then that's a different matter, and it's doing something that Thunderbird is not supposed to do. (But mine does and I can't see why.)

I meant "junk" indeed.

And I wish I could help you. I frequently see non-Junk messages in the Junk folder. So for me it's a problem with routing rather than with mis-classification. (In my case it may be that with my other devices having zero spam control, I am accidentally moving good messages into Junk myself on an Android device.)

Are the notifications marked as Junk, or just inconveniently sent to the Junk folder?

Are you using any filters to automatically move messages? Whilst your filters may be logically correct, mis-operation of the filtering mechanism is another possibility for these lost messages turning up in the Junk folder.

If you are NOT using filters, have you considered doing so? In theory, you can set a filter to operate "before classification", i.e. before the Junk controls can grab it, so you can at least avoid mis-classification issues.

Or a Saved Search folder could be set up to collate these messages, regardless of which folder they end up in. Not a fix, but a pragmatic work-around.

No I was not using filters on this email account.

I'm trying your solution now, I'm good with a pragmatic work-around.

Can you confirm that the 'Personal Address Book' is selected to be a 'whitelest' address book? right click on mail account name in Folder Pane and select 'Settings' select 'Junk Settings' for the mail account.

select ; 'enable adaptive junk controls for this account' Select: various address books to be used as whitelist select; Move new junk messages to' If POP: select: 'Junk folder on' and the mail account If IMAP: select: 'Other' and the 'Junk/spam folder on imap mail account.

click on OK

See image below

yes I had all this set up except "move new junk messages to' which was not selected.

So even using a filter before junk classification doesn't work. The emails still end up in the Junk folder.

I would appreciate any kind of help on this topic! Moving very important emails to the Junk folder is a reason that might make me stop using Thunderbird! I've been using it for years now it would be a shame!

And it's also marking as Junk (although not moving them in the Junk folder) many emails I receive from people who write me daily. There is something weird going on.