This is v2.0 of my mailbox delivery notification system. In this version I scrap the XBee radios, and notification light for an ESP8266 and email notification of delivery. With exception of switching out the Arduino Pro Mini for an ESP8266 and an ATtiny85, all the other core components and construction are the same as v1.0.
v2.0 Code and Schematic
Decent tutorial on setting up Postfix as a relay – I don’t recommend making your server publicly accessible unless you know what you’re doing. If your project does not require secure email, use a service like SMTP2go.
Spark Fun Thing Dev
DPST relay (use/need is described in video).
DS18B20 Temp Sensor
IP67 Rated LEDs
Solar Lithium Ion/Polymer Charger
6V 2W Solar Panel
4400mAh Lithium Ion Battery