I've noticed the dead give away for those is that they come with a "Pre-sorted Standard" stamp instead of the first class postage that most personal mail uses.
I keep getting the same one from a certain car dealership every few months. Apparently handwritten address on envelope, real ordinary first-class postage stamp (even placed at a slight angle, so it doesn't look like a machine did it). Postmarked from a different state than the dealership is in. No return address.
Open it up though, and the deception ends immediately. Just your usual tacky, glossy printed brochure.
