What I would change: get rid of the LoRA, put an ESP32 or ESP8266, keep it powered off all the time, and when I get email, start it, connect to my home wifi (the mailbox is not that far anyway ...

Here in Munich, at Electronica 2018, Arduino has just announced the Arduino PRO Gateway for LoRa. Massimo Banzi, co-founder of Arduino, introduced the new Arduino approach to reducing the complexity ...