1. Keep the message as short as necessary but no shorter.
2. Put the most important information at the top of the message.
3. If it email is for an ask, call out from who you need the response and put it at the top of the message.
4. If you need to send a long email with many details, put the most important information at the top (ie. what the reader needs to know) and then fill in the body with details he/she can choose to indulge.
Example
Hey Jane, I need your input on how to prioritize my current work. Can you provide guidance on where I should focus?
Bug XYZ was assigned to me and it's taking longer to complete because we have a dependency on Vendor ABC completing a change to their web service. This is impacting the commitment to my team on Feature 123 because we are near the end of our sprint.
Lemme know.