ExSp, it isn't your computer that's renaming the files, it is the name that the sender gave it. A campaign should be started to make the geeks aware of the havoc they create in our downloads folders... A com,puter will rename if there is an identical file name there already, buy this will just add _1 as a suffix.
But in the meantime, if you right click with your pointer in the title bar in the file explorer, you can choose more fields. A handy one is 'date created' which is the date it was written to the folder. Clicking on that new title header will order the files by that date, and your newest one should be at the top (or bottom if you click again).