A friend told me he recently received an email from a student looking for an internship in a related field. But the email was so long that my friend couldn’t make out what this kid wanted him to do to help. That’s a shame. The writer probably spent a long time composing all of that information, but in the end, it was overwhelming for the reader and the key message got lost.
When you’re talking to someone, they can interrupt and ask a question if you’ve lost them. Email doesn’t give you that opportunity. So make sure your message is clear. One way to do that is to keep your email to one screen so people don’t have to scroll. I’m not saying you should be curt, just concise. Here is a past post on using email as your introduction, and one on how to write a good message.