Idk what to say to this. Is it true? I don't know, and you probably don't either. That's a weird way to look at it and I doubt anyone has measured the power costs of the global email network.

It's also useless for decision-making. What matters is a question like "how much would it cost me to host a server and contribute to the network?". Even if the total global cost is billions of dollars, the network will continue to grow because nobody has to pay all of it.