Chatting with my parents the other day, they were surprised to learn that almost all of my daily communication is done through e-mail. "Even if someone is right down the hall?" they asked. Yep. Not only is e-mail efficient and asynchronous, but it represents an audit trail to prove who spoke to whom, about what, and when it happened.
E-mail can cause its own problems, though, if you don't know the best way to communicate in this electronic medium. Productivity 501 has a primer on sending efficient e-mail, to which I've added my own insight.
Write from the reader's perspective. Consider the reader's knowledge and experience. Don't assume they know the acronyms and abbreviations.
Include all the background information. Include enough info that you won't have to go around three times just to get enough clarification that the original question can be answered.
Anticipate questions. This can help you include the necessary background information, or perhaps add an attachment.
Keep it short. The longer your e-mail is, the more likely it'll collect dust as the recipient decides to save it for "later" when there's more time.
BLUF -- Put the "Bottom Line Up Front." I learned this from my own mentor some years ago: Don't bury the "ask" at the bottom of an e-mail, after a lengthy preamble or background information. Organize your message so you ask the questions up front, and then add background information afterwards, like that extra info is the appendix to a book.
Photo by Steve 2.0