Email can be a wonderfully powerful tool when used well. Here are tips for email writers from the vantage of twenty years of experience. A friend suggested I label these as "Doug's biases you should know when sending email to him."
Readers will get the point quicker if it's not buried in too much text. Five minutes spent refining a message for clarity may save dozens of minutes clearing up misunderstandings later.
When you limit an email message to one topic, the recipient's decision of what to do with it becomes simpler. It also becomes easier to write a meaningful subject line.
How will someone locate your message and its crucial details when looking for it several weeks from now? Note that distinctive first words are key, as subject fields from lists of messages often show just the first twenty or so characters.
In a message to an audience with varying needs for detail, give the readers help finding the information they need. A summary at the start of the message will often be sufficient for most readers. When they discover they need more details, they can come back and explore the rest of the message. If the complexity is major, a third layer may be appropriate; extract subsidiary details into appendices, as would be done in a book.
Before sending a message, it's a good idea to double-check, "am I sending the right message to the right audience?" Ought these people read this? All of them, as opposed to one or two? Will they? Is email the right medium for the message, given its unreliable delivery, the potential for misunderstanding, and what is known about the audience?
Readers will more easily get the point you want to borrow from a previous message if you summarize it. There is no reason to include entire messages, turning your message into an unwieldy mess. If a recipient does not have a previous message, you can send it separately, as requested.
If your point can be made with simple text, why make the reader go out of the way to start up another computer program? You never know exactly how the program is going to behave, assuming that computer even has it, and you increase the risk having your point get lost to computer gremlins and anti-virus filters. The same is true of fancy fonts and colors, as well as the HTML used to convey them. Plain text is simple, durable and friendly, unlike any other format. You also spend less of your recipient's resources, such as disk space and download bandwidth, which at times may not seem to the recipient as free as it does to you. Even though I may have broadband at home, I'm probably still on a dial-up when I travel.
Is the reader likely to respond to this message as intended? It's helpful for the sender to think through the question, "what response, if any, do I really want here?"
Thanks to Strunk and White, among many others, for inspiration.