Merlin Mann a vocal proponent of David Allen's Getting Things Done wrote some good advice on business email use: email howto a piece of it that is tailor made for me is:
Keep It Short
Finally, when you do respond to your mail, keep your answers as concise as possible. Donât sit on old mail because you dread crafting a long response. Just keep the ball in motion by clarifying, asking questions, offering help, or even saying âI donât know.â? You can always write more later.
Now to practice that.