I was once in a seminar led by one of the world's pre-eminent primate researchers who explained that, without any irony or humor, he refused to scroll when reading emails--Anything important should be immediately visible.
I have been developing my email habits to fit this. If my email is turning into a novel I make a point to bring the important information to the top as a TL;DR. If I forward an email chain longer then two emails I condense the email chain in my forwarded email so the reader sees and understands exactly what I need them to see. I have found that if I forward a long email chain/write a novel of an email no one reads th…
Try not to pass the cognitive load to others. Make them do as little work as possible -- be computationally kind.