An SMS, an instant message or an email don’t share the same environmental impact. This happens because they don’t use the same technologies. Whereas SMS use the frequencies of conventional telephony, instant messages and emails use internet data flows. These are different ways of processing data that spend different amounts of energy.
An SMS with a maximum weight of 140 bytes emits 0.00215 g of CO2 (based on the data provided by Vodafone) compared to a simple average email that emits 4 g of CO2. Hence, we can say that SMS uses less energy and emits less CO2 than emails. So go Old School and SMS!