this is good advice, but I'd also include a "teaser deck" as an attachment. I've had great luck with ours - it basically boils your entire company down to a story that you convey with no more than 5 slides. Each slide has an image and no more than one sentence/thought. Most people don't read more than a few sentences of text in an email, and the ultimate reductionism required to get to a good teaser deck is great practice for refining your own thoughts. Use the teaser deck to get the follow up meeting or call, and that's where you can dig in and explain.