Something that I come across often when it comes to emails is people who don't respond to the question/s in my initial email. I find this ineffective, because it usually means that I have to send a follow-up email and they have to respond again.
When I have to write a long email, I usually let the reader know that it will be long but important, or I flag it as extremely important. I also use bullet points, and also highlight questions I need answers to. I also color code, bold, etc. I send follow-up emails as well. These tactics help, but don't always work.