A. Alphabetize the inbox and search under Wfor Widgets-R-Us
Explanation:
The best way to begin the search is to narrow it down as much as possible and this is what option A does. In alphabetically arranging the inbox, the communications from specific addresses would show up as an alphabetically ordered list.
One can then go find the address they are looking for and find all the correspondence with that email address. The other options are much too tedious and will take more time.