@neil
A large PLC that I consult for insists on attaching a 32kb image promoting their environmentally conscious efforts to email, not just the first one in the thread, and not just externally either.

The maths is over my head, but I conservatively estimate that my Outlook #macro that strips attachments from emails has probably saved them more money and reduced more carbon than any of the green initiatives in their list. (And yes, I do actually get that many emails from various departments).