Mount an ESP32-C3 Super Mini with a reed switch on the mailbox door (or a VL53L0X time-of-flight distance sensor inside the box), flash it with ESPHome 2026.3, and wire it into Home Assistant - you will get instant push notifications on your phone the moment mail lands. The total parts cost sits under $15, and deep sleep keeps the whole thing alive for months on a single 18650 cell.
This is one of those projects where the payoff-to-effort ratio is absurd. Twenty minutes of soldering, a few lines of YAML, and you never walk to an empty mailbox again.






