Check Your Mailbox Using The AirTag Infrastructure

A small round NRF51822 board glued to the underside of a mailbox lid, with a small vibration sensor attached

When a company creates an infrastructure of devices, we sometimes subvert this infrastructure and use it to solve tricky problems. For example, here’s a question that many a hacker has pondered – how do you detect when someone puts mail into your mailbox? Depending on the availability of power and wireless/wired connectivity options, this problem can range from “very easy” to “impractical to solve”. [dakhnod] just made this problem trivial for the vast majority of hackers, with the FakeTag project – piggybacking off the Apple’s AirTag infrastructure.

This project uses a cheap generic CR2032-powered NRF51822 board, sending the mailbox status over the FindMy system Apple has built for the AirTag devices. For the incoming mail detection, he uses a simple vibration sensor, glued to the flap lid – we imagine that, for flap-less mailboxes, an optical sensor or a different kind of mechanical sensor could be used instead. Every time someone with a FindMy-friendly iPhone passes by [dakhnod]’s mailbox, he gets an update on its status, with a counter of times the sensor has been triggered. [dakhnod] estimates that the device could run for up to a year on a single battery.

a NRF51822 module in a 3d-printed case, with a copper strip used for holding a CR2032 batteryThe specific NRF51822 board shown in the title picture seems to be sold for about $7 online, but there are many different NRF51822 boards available, and you should be able to use any one of them. As an example, [dakhnod] sends us a photo of a different sensor he designed, held in a 3D printed case and connecting to a CR2032 battery using copper tape. By now, it’s not unlikely that a friendly hackerspace has a few suitable boards in a drawer somewhere!

This project builds on top of the OpenHaystack project, a research effort that we’ve previously told you about. We’ve even seen the ESP32 microcontrollers being used for building clones before, but the NRF51822 low-power features are unbeatable for practical applications.

32 thoughts on “Check Your Mailbox Using The AirTag Infrastructure

    1. There is a wrinkle – OpenHaystack, which is the tool used to retrieve the tag data, needs to run on a MacOS device so it can commandeer the privileges of Apple Mail to access the necessary API. So yeah, it’s not exactly wide open.

    1. In my old home I had just that. I also had a cat that was a keen mouse hunter, and liked to bring the prey back home to eat on the door mat underneath the post flap.
      Post covered with mouse gutts and blood was a regular occurrence.

    2. Postal carries rarely go an actual door for most of the US anymore. You must either have a mailbox at the end of the driveway, or for newer neighborhoods there are central post boxes. Even some older neighborhoods are getting retrofitted and losing their personal mailboxes.

      1. Ours in at the end of our side walk next to the street. The mail person will still come up to door to deliver packages that don’t fit of course. Our son’s family in Florida get theirs at a central post for the housing development they live in. Seems ‘weird’ to us.

      2. I had thought that was a rural thing, but then I’m in Canada.

        Some areas have centralized mailboxes, so people go to the corner to collect their mail, a key is needed. A few years back there was a pkan to implement that more generally, but itne er happened.

  1. Clearly not a Canada/USA project – if it were, the vibration sensor would constantly sense false positives from over-compensating truck drivers passing by…

  2. I use a yolink motion sensor in the mailbox. I get a silent alert on my phone when the mail is delivered. Works great. Yolink uses it’s own hub, but if you buy 4 leak detectors, you get a hub with them. Then you can add a motion sensor inexpensively. Probably not the best stand alone solution. At six months, battery still shows full. Recharge needed less than once per year.

    Aside: I use yolink temperature/humidity sensors to control fans in the closet where my internet and IoT rack is and in a cabinet with a media pc. High temperature alert turns on the fan, low temperature turns off the fan. You have to use their switches to make this work, which are more expensive than competing brands but has worked well for me.

    1. That’s exactly what I am using – a YoLink Motion Sensor inside our mailbox which is mounted on the wall of the front porch. At first I tried a YoLink Sensitivity Sensor but it went off everytime the front door was opened and closed. Amazon’s customer reviews of the Yolink Motion Sensor reports dozens of people using this exact sensor inside their mailbox. I also set up an Alexa routine which plays a little trumpet sound and “You’ve Got Mail” ala AOL. LOL.

  3. We have a locking mailbox provided by the Post Office, that serves all the houses on our cul-de-sac. It’s all metal, so makes a good Faraday shield. So great for security but not so great if you want to transmit status with RF.

    1. You’d be surprised how *not* good a simple metal box is as a faraday shield. You’ll get attenuation, but modern devices can have so much link budget (via reception sensitivity rather than transmission strength) that unless you go over every single gap and seam of your box with conductive mesh tape, a significant amount of signal will still escape.

      I had the *worst* time trying to do testing of an ultra-low-power cellular device that needed to be prevented from reaching the network without a proper rf shield box. A regular metal box was insufficient. Replacing the antenna with a dummy load on a pigtail was insufficient. I had to solder a dummy load resistor directly onto the PCB to reduce the loop area sufficiently that it would no longer connect.

    1. USPS has a free service called informed delivery you just go to their site but your name and address in and you get daily emails that show the front of the envelope of any and all mail delivered to you and a lot of times it’s even a day early if it’s in processing so that way if it’s just junk mail you know you don’t have to bother. PO boxes are also now included

      1. I have Informed Delivery and appreciate it. However, I live on a large development in Texas and it is two miles to our mailboxes. It would be nice to know when my mail is delivered so I won’t have to make a four mile round trip for nothing as has happened in the past.

  4. Or for even less than $7 and the ability to see if the mail you got was even worth stopping to pick up that day versus just junk mail, USPS offers a service you just put your address in and you get daily photo images of the front of the envelope of anything that was delivered that day. Better yet you can actually see it about a day ahead of time and it’s getting scanned in for processing. It’s actually pretty useful

  5. I have a hex nut tied to a piece of red felt. I set it with the felt hanging outside the box. The lid holds it in place. When the mail is delivered and the lid is raised, the nut falls inside and the red felt disappears. Real easy to see from inside the house.

  6. I was wondering about why this information was of much importance to most people and why it would be. I’ve had recently been what I believe to be a number of “harassing “ letters just put in my mailbox w no stamp or not run through the postal service just “dropped off” and leave…. Along with notes put on my windshield along w my assistants car…. Even after asking to not do so, or to just come and try to speak in person, it continues to happen and had heard that it was actually illegal to run such letters or notes in an envelope through Amy personal freestanding mailbox in front of my home. This would be something possibly of use….? Is that enough and does anyone know any further actions to be done to stop such a way to allow that person to what I believe is an inappropriate way to communicate their negative emotions and feelings about such situations that need to be handled in different ways.?? Thanks so much.

  7. You know your local Best Buy Carrie’s a handy device made by Ring called a Mailbox Sensor…Most people have a Ring Doorbell or device similar in which the same network could be used to do the same thing…

  8. You all know you can subscribe for free to USPS Informed Delivery right? It’s not well advertised but essentially you get a photo of every piece of mail being delivered that day. And you can go back up to a week to see all the mail you received if say you are out of town. Basically as they’re scanning your mail a photo is taken and that’s what they show you via the website. You’re welcome.

  9. Do you think you could similarly attach a 3-axis accelerometer to the NRF51822 board rather than a vibration sensor (and sends this over the FindMy)? Then you could have a device that senses a more complex array of movements

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