Normally Thunderbird automatically creates a 2025 subfolder in Archives when you archive any email received this year (select email and type A or click the Archive button). Do you use a filter for automatic archiving?

@Mapenzi Yes, that's how I archive, but I'm not sure if I have any automatic filters. Now you mention it, I do remember looking at those once.

Where would I find these? I had a quick look but can't see where they would be set up.

Thanks for the reply.

Ah, found them.

No, I don't have any automatic filter rules that would affect this. The only rules I have (which are now obsolete) are to do with auto archiving messages from a nightly job that no longer runs. I can see from the log that the rules hasn't been applied for almost two years.

Thanks anyway, any other ideas?

You can verify if you have set filters or not by going to Tools > Message Filters... If you archive any message from 2025 doesn't Thunderbird create the 2025 subfolder?

If you archive any message from 2025 doesn't Thunderbird create the 2025 subfolder?

No, that's the whole problem. I've been archiving messages as usual, and only just noticed that TB didn't create a 2025 folder, and is putting them somewhere else, but I can't see where.

Do a global search for one of those 2025 messages you have archived. In the list of results you can find where your messages have gone by activating the "Location" column, if necessary the "Account" column, too.

Ah-ha! Whilst doing what you suggested, I remembered that in order to get the number of messages showing next to each folder, I had to go to the folder properties and select which folders were included. I went back there and saw that 2025 was there, but not checked. I checked it and the folder appeared as expected.

Thanks very much

Your solution is surprising because the number of messages showing next to each folder cannot be activated via Properties. I guess that this is an IMAP account and you had to click on the Account name > Subscribe .... and then in the Folder List check the 2025 subfolder. But anyhow how you arrived there it's the result which counts!