In "How to Improve Your Business Writing" by Carolyn O'Hara for the Harvard Business Review, you will find a practical summary of the writing product (your completed emails, analyses, reports, and proposals) and the writing process (the method you use to transfer ideas from your brain to your computer screen or paper).
Even though the article appeared nine years ago, it covers enough ground to serve as a primer for developing business writers. O'Hara concludes with two relatable case studies to reinforce the principles she raises, such as planning messages thoroughly, writing clearly and concisely, practicing continually. For a five-minute read, that's a heap of worthwhile information.