I just went into my mail as I often do and clicked on the Red Flag filter. Strangely, it's showing four random messages from my ancient history, none of which are flagged. It's not showing the dozen or so messages I know I've flagged recently. On these incorrect messages, no red flag appears on their entries. If I go and flag a new message, it correctly appears along with the 4 incorrect ones.
I tried making a new Smart Folder but it shows the same thing.
This did not coincide with any key events, like updates and whatnot. Actually it did happen around the time the system reported my HD space was running low, but I emptied my bin and have plenty for now.
Incidentally, my "Unread" button in the nav bar disabled itself several weeks ago, but I was able to work around that by making a Smart Folder.
Is there a way to just reset/reindex the whole thing? "Rebuild" didn't seem to do much (nor did it take very long).