Suddenly a search for an archived email searches not only the selected folder, but also all other folders, and the internet - how do I get rid of this feature?

It used to be simple to find archived emails, by designating a search term (eg, "Susan"), selecting a search field (eg "From") and searching within a folder (eg "accounts"). Suddenly, presumably as a result of some upgrade, there is no way to limit the search field, so "Susan" appearing in any part of any message will yield a hit. Also, the default search strategy includes all folders (even when I already know which folder to search) as well as the internet. I cannot seem to find any option to remove this whole-world search feature, and I cannot find any place in Preferences to adjust this search strategy, nor any way to apply limits prior to running the search (meaning that I have to wait for the whole world search to complete before I can delimit the search to a particular folder, each time). Can someone tell me how to remove this whole-world search feature, and restore the one that only searches the folder and field I designate?