Explore how to build an open-source, self-hosted mailbox notification system in this 23-minute tutorial. Learn to create a gadget that alerts you when mail is delivered, eliminating the need for frequent mailbox checks. Discover the physical setup, including hardware components and switch installation. Observe the notification system in action and understand the code used to run it. Gain insights into using tools like Ntfy for sending notifications, Raspberry Pi OS Lite for the operating system, and optional software like Angry IP Scanner. Follow along with timestamps for easy navigation through different sections of the tutorial, from introduction to code explanation.