Why the fuck are they posting this bullshit? The cost of an email include the cost of the device you use to send or read the email, which is 70% of the cost. Then it's 15% (energy wise) to transport the email. The cost of storing the email is 0.5%.
With that in mind, think about how much it costs to watch 1h on YouTube or Netflix...
Some explanations in French (sry):
Signal Proxy is fine, and it's helpful for people who live in countries that block Signal. I ran it during Iran revolution. It's only a nginx forward proxy.
Tor exit relay is a big no-no since you may expose yourself to illegal content. But you can run a relay without it being an exit node.