That would be targeted to individual(s) not "all email from everyone" NSLs target a service or an individual or a corporation. Bad as that is, it's not intercepting, storing, scanning every email.
I suppose it's how you choose to interpret other people. They may not read everyone's email, but they certainly can read anyone's. This was always the scary part to me.
National security letters target individuals and aren't sent in enough volume to cover more than 0.01% of "everyone's emails".