They can delete your e-mail with a single click. If you don't communicate effectively with your audience, you'll never achieve any of your other online publishing goals. Your readers want you to make sense, and to talk about things that they care about. Above all, they want you to be honest. As the term implies, business people are busy .
Plain language communicates well to all audiences, including business audiences.
That said, many business people think they prefer to read business-ese. However, that's often because business-ese is the only language they know how to use. Give them the choice. Show them what's possible. Address the issues that your readers will care about, and try to answer whatever questions they are likely to have.