The matrix of power can help out here. The most powerful person according to the matrix has to communicate as everyone relies on their orders and so is mostly listened to in the whole project team. The most information with no emotions can be safely shared via email. If you want to share your latest sales reports or schedule a time to get together, email, memo, or instant message are great ways to do it. You’re communicating information. Your reader won’t be having an emotional episode while reading. Most work communication is facts and figures, so email is best for that.