Over the many years that I've worked in an office and also owned my own company I've consistently been complimented for my well-written and well-thought out emails. This doesn't just happen by accident and I've found a simple tool in OS X that can help everyone. Before you send that important email, highlight the text and go to Mail > Services > Speech > Start Speaking Text. You'll probably be amazed to hear missing and misspelled words that your own proofreading missed or even juxtaposed words and phrases. I've also found that while this service isn't available per se in MS Word for example, you can copy and paste the text into a new mail message and get the same benefit. Good luck!