Pssst—hey, kid. Do you want to save fifty cents every time you mail something from the post office? You do? Then gather ‘round and listen closely.
As you’re probably aware, your local U.S. post office provides customers with free envelopes and boxes of different sizes for sending items via priority mail. For a flat fee, you can mail just about anything* you can cram into one of these containers, as long as you can seal it. Pictured below is a USPS priority mail Small Flat Rate Box. You can ship it from your local post office to any address in the U.S. for $8.45.
Comparatively, for $7.95 (a full 50 cents cheaper), the USPS will send this Small Flat Rate Envelope to any address in the U.S.:
But you may not have realized: The box fits inside the envelope, and it seals up tight, and the cost stays at the same cheaper rate.
Therefore, if you need to protect your priority mail with a sturdy cardboard box, you can seal your precious cargo in the box, slip the box into the envelope, and walk away from your local post office with an extra $.50 jingling in your pocket.
While the post office doesn’t advertise this “feature,” according to my local mail clerk, there is nothing illegal or unscrupulous about doing it. But if you want to get ethically nit-picky, it does use way more useless packaging than sending the box on its own, and that means more trees have to die. But if you’re OK with that, go for it.
*You cannot mail airbags, ammunition, explosives, gasoline, marijuana, cigarettes, and other forms of tobacco at all, and there are thousands of things with shipping restrictions, including cremated remains, leeches, emus, and radioactive material. (Full list here.)