I love Matthew Stibbe’s blog Bad Language because it is so crisp and clean and useful.
He has an excellent post on writing emails that you should all check out. It does not contain earth-shattering information that you have never heard, but it is crisp, clean and useful. Kind of like your emails should be but aren’t.
A favorite line:
"Don’t drunk-mail. Don’t email when angry. Don’t argue by email."