[MlMt] Not working: "Include messages in any submailboxes of this mailbox" (MM r5865 on macOS 12.1)

[Sam Birch]

I’d like to have a smart mailbox that includes messages from all subfolders of a particular IMAP folder. So I’ve selected that IMAP folder in the “Mailboxes” tab. Since that folder contains no messages itself (only subfolders) the smart mailbox is initially empty.

The problem is that checking the “Include messages in any submailboxes of this mailbox” checkbox has no effect — the smart mailbox remains empty. Furthermore, the checkbox clears itself if I switch to another tab or close the mailbox editor.

This looks like a bug, but maybe I just don’t understand how it’s supposed to work. Any ideas?

Cheers,
-sam