Let’s see, it all started with somebody wondering if you can get a letter back from the postal service once it has been mailed, but before it has been delivered. Maybe you changed your mind about sending the letter, for example. I still don’t know the answer, but I’m guessing if there is no return address on it, forget it. If there is a return address, however, it ought to be possible, right? The sender will get the letter back normally in the case that it is undeliverable, so the sender is essentially a secondary recipient. What does the postal service do with undeliverable mail that has no return address anyway? Shred it? Anyway, this doens’t seem like a satisfactory conclusion in any case, that the return address should play an unrelated role in the mail interception problem.

Which brings me to the second topic. If we abstract away the implementation details and take the return address to be a bona fide secondary delivery address, then we can do some unexpected things, for example,

• What if put the destination address in the return address position and put a bad address in the destination address? The mail still gets delivered…
• But wait, undeliverable mail is only one of many conditions for returned mail. Insufficient postage is another. So don’t even bother putting a stamp on there…
• Now, sometimes, the postal service delivers the mail anyway, so for recoverability, swap the return and destination addresses; this way, you at least get the mail back if USPS is too nice.
• Even better, for automatic redundancy, put the destination address in both the return address and destination address positions, so no matter what, the postal service delivers the mail.

Wow, I like this already (“this” being the idea, not actually doing it). If Wikipedia is to be believed, the blatant scam in the last scheme is actually legal and works. But I’ve also heard the postal service sometimes delivers with insufficient postage but bills the recipient for postage due mail.

The few times I messed up with first-class postage raises, I’ve got mail back with insufficient postage. Which makes me wonder about the the price of first-class postage. In 1993, it was $0.29. Today (2006) it is $0.39. That’s pretty much in the inflationary range. With the proposed hike to $0.42 next year, there is also this new thing:

The post office is planning a ”forever” stamp for letters, good no matter how many times postal rates increase. That means people could say goodbye to those annoying 2- or 3-cent stamps that have to be added to letters every time rates go up. The idea for the special stamps, which would be sold at the same price as other first-class stamps, was included in proposals announced yesterday that would also raise stamp prices 3 cents — to 42 cents — next year.

That’s nice, you can buy floating-value stamps. The comments that follow in the link are even more interesting…(*) I’ve never seriously thought of postage stamps as a money instrument before. Of course you can buy them on ebay and sometimes stores for a discount (never understood where the discount comes from… value of liquidity?), but those are not as explicit as the derivative market that may result from the trading of “forever” stamps just before and after a rate hike. Can you imagine the run on “forever” stamps before a rate hike by arbitragers and eBay hawkers? Will there be a ration or what? Or as somebody in the comments suggested, they really shouldn’t be sold for X months prior to a rate hike (X depending on interest rates and percentage of hike). Let’s see how this pans out. I still send first-class mail, after all, even without the interest in derivatives.

Actually, when I first read about “forever” stamps, I was confused, because I’ve seen non-denominated stamps before that just say “First Class USA” and I had wondered whether they acted like “forever” stamps. I’ve just assumed they had whatever value they were purchased at. Of course this is correct – they are distributed right after a rate hike before stamps with the newly approved price is printed, and are worth the price at the time of purchase. But it must get confusing, if not for the postman then certainly for me… recently there has been a plethora of flag designs… I can’t remember which is which. Well, here are some that I recall seeing fairly often and recall wondering about their values:

$0.05	$0.10	$0.10	$0.25
$0.29	$0.32	$0.32	$0.33
$0.34	$0.37	$0.39	$0.41

More of them here. All right, that’s it.

(*) There is some mention in the comments about some arbitraging scheme of postages denominated in different currencies. This is a nice idea that actually has some applications in online forums, and will be discussed in another post.