I know, I know—that’s schoolmarm talk. But I’m serious here. It’s important for you to be aware of which style you use.
Active voice—to the point, engaging, and, well, active. The subject of your sentence is doing the action. For example, “The dog cornered the rabbit in the old abandoned shed.”
Passive voice—roundabout and sometimes dull. The object of the sentence (the thing being acted on) gets to star. “The rabbit was cornered by the dog in the old abandoned shed.”
Nine times out of ten, you’d be wise to choose active over passive voice. It’s clearer, it gets the audience to the point (without their having to do excessive work) much faster, and it’s more fun to read. Plus, active voice typically uses fewer words, which, following my theme of “cut, cut, cut” when it comes to business emails, will mean less clutter on the screen.
There is that one time out of ten, however, when you might purposefully choose to use passive voice. For example, if you think your reader will feel attacked by your message, you might use passive voice because it could feel safer to your reader, which could garner a less angry and perhaps even more favorable response.
Just remember not to combine the two approaches. A mix of active and passive voice can become frustrating for a reader and might make you seem, by turns, confident and afraid. Choose the style you will use and be aware enough to stick with it through the entire email.