Why Does the Post Office Deliver Mail That Has No Stamp?

If you had asked me that question a week ago, I would have said with great certainty that the post office would not mail a letter without a stamp.

A few days ago, however, my daughter got a letter delivered in the mail. Where the stamp should have been, the sender had instead written, “Exempt from postage: Guinness Book of World Records attempt.”

The envelope contained a single sheet of paper, describing an attempt to set the record for the world’s longest running chain letter, along with instructions to pass this letter along to seven friends. If we broke the chain, the Postal Service (which is monitoring the record attempt) would know that we were the individuals who ruined it for all of the people who had been part of the chain since 1991!

The simple arithmetic of chain letters guaranteed that somebody was lying.

A chain letter for which every recipient actually forwarded the letter to seven other people would quickly absorb every child in the world (7 raised to the power of 10 is roughly the U.S. population.) I did, however, give the sender credit for at least admitting this was a chain letter.

The thing that puzzled me was why the Postal Service was aiding and abetting this effort. It seemed bizarre, but at the same time lent credence to the endeavor. Maybe this really did have something to do with a world record bid.

A quick Google search, however, revealed that the Postal Service isn’t condoning the chain mail. Actually, the explanation for why the letter got delivered without postage is even more interesting to me: apparently the automated mail sorting machines fail to catch many letters that are missing a stamp.

On reflection, this does make sense — profit maximization requires setting the marginal cost of an action equal to the marginal benefit. If almost all letters have stamps, then the benefit of checking each one with 100 percent accuracy is infinitesimal, so it makes sense to let some unstamped letters through. (The same idea holds for catching people who don’t pay their train fare.)

Now I am curious to know exactly how lax the Postal Service is. Perhaps some blog readers with plenty of extra time on their hands can experiment with this by sending a bunch of unstamped letters and see how many make it to the destination? We will report the results here on the blog if someone rises to the challenge.

I’m just about to drop something in the mail. Maybe I’ll skip the stamp — though I suspect my tax return will make its way to the I.R.S., stamp or no stamp.


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  1. discordian says:

    you want to send a letter without postage?
    address it to yourself with the return address to who you really want it to go to.
    Then USPS will “return” it for lack of postage.
    Or you’ll get it back the next day to try again.

    Either that or just send an email.

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  2. AaronS says:

    Hidden due to low comment rating. Click here to see.

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  3. Steerpike says:

    I’m pretty sure that here in the UK they just charge the recipient. The postman simply fines the person to whom the unstamped letter has been sent – otherwise he will not hand over the letter.

    Whether the marginal cost of recouping this money (which is measured principally as the deliverer’s lost time) is greater than just delivering it, I have no idea.

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  4. Speedmaster says:

    Pure altruism? 😉

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  5. grace says:

    i’ll be trying this in singapore. i’ll let you know. :)

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  6. DJH says:

    A number of years ago I worked in a mailing operation at a savings & loan. We sent out between 250k and 400k pieces of mail per month. Even with our automated equipment the occasional piece of mail went out without postage; I know that some ended up being delivered, although we always got a small number that USPS returned for postage. I could count on one hand the number that arrived at the customer with “postage due” (and I know that ’cause said customer invariably complained loudly about it).

    On at least one occasion in 1993 we sent out c. 1,000 pieces, all at once, without any postage. About 200 were returned. As far as we could tell the rest were delivered. Of that batch, oddly enough, we received not one complaint about “postage due.” What makes this particular event remarkable is that the entire block of unmetered mail made up the contents of two letter-trays; they were all together. So why did the USPS choose to send some along, but not others? It would have been much easier on the letters’ handlers to scoop them all up, together, and return them in one block, just as they had been delivered … so I can’t attribute it to laziness.

    Go figure.

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  7. Mark B says:

    Are you using your blog to call for theft of service? I’m not against it, I was just curious.

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  8. ottan says:

    While I am not a huge fan of the USPO, it does seem like it is critiqued somewhat unfairly. If FedEx were required to ship most anything and everything that showed up at it’s stores, rather than using their few envelope/box choices, I doubt they would be as efficient as they are now. Like Amtrak, the Post Office is hamstrung by requirements placed on it by the government, but then they are also expected to be efficient.

    Back to the original post, I have occasionally received mail without postage or with insufficient postage (which is more frequent). I always assumed there was some sort of spot-checking system in place to encourage people to post correctly.

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