PO Box vs. Street Address: Does the USPS Have a Preference?

The "Fast Lane" Answer

Does the USPS have a preference? Yes.

Because PO Boxes are at the post office, delivering mail there is pretty much as simple as taking it out of the bag, reaching over, and putting it in the slot. That may be a bit of an oversimplification, but it drives the point home. With PO Boxes, the USPS doesn't have to transport the letter to a separate location, which saves them time and money. So it's safe to say they prefer keeping things close to home.

The trucks still go out, though, and the postage is the same either way, so if you know what you're doing, you can still get your mail delivered to the front door. If you have a preference (whether PO Box or mailbox), getting post is just a matter of knowing how to tell the USPS where you want it to go.

Caveat: some rural locations only have PO Box service, i.e. they don't deliver directly to the physical address. In these cases you'll have to send to the PO Box. Sorry.

The "Scenic Route" Answer

But does the USPS really have a preference? Not really, no.

While the postman would love to simplify his route by merely dropping your letter in a PO Box right there at the home office, this preference won't prevent a delivery from reaching someone's front door. Unless the physical address is in an area that is not serviced by the USPS, you can get your letter mailed to either the PO Box or to the physical address, according to your heart's desire. The trick is knowing the USPS's secret spy code. And we're about to hand you your decoder ring.

Are you ready to learn the secret code? Ok, lean in real close so no one else can hear. Its so super-clandestine, you won’t even find this in the USPS’ Publication 28.

They send to whichever address is listed on the first address line.

It really is that simple. Here are a couple of examples:

Address Line 1: 1407 Graymalkin Lane
Address Line 2: PO Box 42
Last Line: Salem Center, New York 10560

This address would ship to 1407 Graymalkin Lane, because it's in the first address line. See, the USPS only considers the first line to be the actual "address", while the second line is merely information that's beneficial for the delivery person, not the person sorting the mail. Now let's look at the reverse:

Address Line 1: PO Box 42
Address Line 2: 1407 Graymalkin Lane
Last Line: Salem Center, New York 10560

This letter, as you might have guessed, isn't leaving the post office. The physical address is treated as being superfluous, and the letter is tossed into the the PO Box (from across the room, if the guy in the blue shirt has good aim).

It's as simple as that. Tell them where you want it to go, and they take it there.

Now at this point you might stop us and say, "But hey, what if I want to throw them a curve ball, and put it all on one line? What path might my letter follow then?" To which we would answer, "The path of least resistance." Observe:

Address Line 1: PO Box 42 1407 Graymalkin Lane
Address Line 2: (blank)
Last Line: Salem Center, New York 10560


Address Line 1: 1407 Graymalkin Lane PO Box 42
Address Line 2: (blank)
Last Line: Salem Center, New York 10560

You might think you're being clever or nefarious, but in reality the USPS flat-out refuses to play your game. They look at it and think, "That's not how an address is suppose to look. I'm just going to go ahead and fix this." (This, by the way, is called "standardizing," and there are actual standards that addresses have to meet. [/articles/standardization-and-validation] As address validators we standardize addresses for people all the time. You might say we address a standard problem.) In the end, the postman will make either of the above offerings look like this:

Address Line 1: PO Box 42
Address Line 2: 1407 Graymalkin Lane
Last Line: Salem Center, New York 10560

Which means it's headed for a PO Box. In other words, when you give them the option, they do indeed prefer to just aim for that box across the room and give it a toss. That doesn't ever stop them from doing what you tell them to, though.

One last thing: we mentioned the whole "some places only have PO Boxes" thing. This is kind of important even from an address validation standpoint, and we'd like to explain why.

Sometimes the USPS doesn't service a city the way they do in other locations. Usually in rural areas, they may require people who live there to sign up for a PO Box and have their mail exclusively addressed to that box. That means that their home and business addresses aren't even on file with the USPS (at least not in the same way), and if you ask the USPS if one of those houses is a real address, they will shrug and say, "We don't think so." Since address validators build on the USPS data, we'll give you the same response.

Let's look at two more examples to illustrate:

Address Line 1: PO Box 1492
Address Line 2:16346 E. Graham Circle
Last Line:Palmer, AK 99645


Address Line 1: 16346 E. Graham Circle
Address Line 2: PO Box 1492
Last Line: Palmer, AK 99645

Because the USPS primarily looks at the first line, the first example would register as a valid address, and they would deliver the mail to the box (hopefully on the first throw). They would ignore the second line, which their system wouldn't even recognize, because that information is purely supplemental.

The second example, on the other hand, would come up invalid, and would be returned to sender. Let that one sink in, folks: You can actually have a letter returned to you for improperly providing too much information. Just like with the first example, the mailman only really looks at that first line to start with. When that one comes up as invalid, he doesn't look down at line two for clarification—he would have just left that line for the actual mail carrier who takes the letter out for delivery. The person sorting the mail would simply accept the first verdict, and send it back to you.

If you're nervous about this, and want to avoid potentially invalidating your address, you can always throw them that curveball from above by combining both the street address and the PO Box on the same line. They'll sort it out just like normal, delivering the post to the PO Box as if you had put that on line one.

So there you have it, your secret decoder ring for determining how to send to PO Boxes and street addresses. We're sorry there's no caramel popcorn to go with it.