A search on Messages, at the very minimum, searches the folder in which you are focused plus ALL its child folders and their subfolders. If memory serves, it will not search in the folder tree above where you are. But if you're sitting at the inbox level everything else is either at that level (and gets searched) or below it.
I'm talking about the standard CTRL+E search. You can exercise additional control in the advanced search, but I only use that once in several blue moons.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
There are many who labor under the gross misapprehension that the Constitution is a cage and a laundry-list rather than a framework upon which great things have been and still will be built. Many things that are entirely Constitutional are not "in the Constitution," but are allowed under it.