There are extraordinarily few actions that can be taken by just a small group of people that have more than a vanishing impact on carbon emissions. But that doesn't mean that these actions shouldn't be taken.
Unless you provide any numbers I think most people would rather enjoy life than think how many nanograms of CO2 they’re releasing when sending an email.
Yeah, maybe the email provider should think about how many tons their equipment causes. Shoving everything on the consumer is silly. Consumers almost never have the data to make informed choices.