A mailbox alert system informs you when you have mail. The system is typically attached to the mailbox so it can send the alert when the mailbox is opened. Depending on the type of alert used, the device home mailbox sensor may be connected to an indoor receiver. If you’ve ever checked the mail repeatedly only to find it empty, or your mailbox is a good hoof from your house, this project is for you. It’s a simple photo-sensitive alarm that will fire off an SMS message to your phone when the mailbox is opened and the sensor is triggered.The video above shows you how it works, and while it definitely requires some specific electronics to make it work, it’s nothing you can’t do easily with a little effort. Here’s how Instructables user nikoala3 describes it. This instructable will show you how to make a web-connected mailbox sensor. Besides emailing you when your mailbox is opened, mailboxsensor.com it will also signal a Raspberry Pi sitting in your house to play an audio announcement. There is also a web-accessible Android/iPhone interface for you to check what time mail was delivered, as well as display the battery voltage left on the sensor.But this could also easily be used as a web-connected security system, one that both plays an audio alarm in your home and emails you when the someone breaks into your house.Under normal use (a few door openings per day), the battery powered mailbox Arduino should last over a year on a set of 4xAA batteries. The transceiver has a range of over 700 feet through multiple walls, so this http://mailboxsensor.com should work for most situations.Take a look at this longer video to understand how the pieces of this system talk to each other. Then, we’ll start the first step of making the Mailbox Arduino.