Junk is sometimes labelled as such by the server at which they are first received. TB may only be following the labelling that is being received. Have you checked how the online account has marked the emails?

Have you been marking emails designated 'junk' as 'not junk'? If you are, does the same sender have their emails marked again as 'junk' the next time a message is received?

Thanks for your reply. My server does mark them, and I don't have any problem with that showing up in Thunderbird. In fact, that is quite useful. The problem I'm having is that Thunderbird moves them to my junk folder, even though I set it to not do that. I had it set to move them before, but it was more annoying to have to check the junk folder, because it seems no amount of training (months of it) got it to recognize things properly. All I want is for it to stop moving the mail. Have I missed a setting? In the main Settings > Privacy & Security > Junk, I only have "Mark messages as read: When manually marked as junk" checked. The other settings are not checked and greyed out. In each account, in Account Settings > Junk Settings, everything is unchecked and greyed out. Any thoughts?

Any thoughts?

Only that I haven't got my head round how the Junk set up works in TB yet. I get some Junk emails (TB recognises this as junk) arrive in the Inbox folder. I do get Junk I've marked as Junk turn up in Junk - and also Junk assigned as such by the server turn up in Junk.

But some allocations do seem strange. It's not a hassle for me as I don't get many emails but I can see it's a problem for you.

I don't think it's a setting (but what do I know?), it's just a querk.