I imagine it is just one of the curses for people that simultaneously think and type too fast. My emails are regularly too long, and I understand that. I pray that you are a good skimmer, because I'm incapable of ridding the text of all the details I deem necessary. Yet, I've learned time and time again that NOBODY is a good skimmer.
I understand. Most of us went to college (or at least finished high school). We're handed a baker's dozen of textbooks and expected to read a chapter from each every night. It's way easier to read the questions at the end of the chapter and find the answers via highlighted examples or our mad honing skills. We've been trained to do this for years, even though nobody seems to do it well.
This is a little hypocritical of me, since I have certainly done my fair share of 'kind of reading' textbooks throughout college. I expected things to change a little when I entered the real world. After all, emails from colleagues about upcoming meetings are way more important than that chapter on the unit circle, right?
My emails are important, and should be treated as such. They are from me, after all!