Perhaps this has happened to you. You are sending an out-of-the-blue email to someone you would like to introduce yourself to or ask something of. You work diligently on the email, read it over several times, maybe even wait a day, and then send it. Shortly after you hit the send button, you realize that your email was too long, you gave more information than needed and probably scared/numbed the recipient away. Shortly after I sent one of those I came across the Email Charter.
Here's number 1:
Respect Recipients' Time
This is the fundamental rule. As the message sender, the onus is on YOU to minimize the time your email will take to process. Even if it means taking more time at your end before sending.
The Email Charter