Sue Hershkowitz-Coore is one of the most in- demand workshop and keynote speakers in the US. She has an interesting site (SpeakerSue) full of useful information on communication. She also publishes an email Ezine with many useful tips.
Here is the link to an article on “Boost Influence! 8 Tips to Get Best Results in Email”
And if you think you will never be able to publish a book, take a look at her short video