When you write an email message to a smaller group, you are likely to have a specific purpose related to the work of that group. We noted these possible purposes:
If you're using email messages to initiate group brainstorming, you'll want to include in your message not only what you see as the goal of the group work (for example, we are looking for solutions to problem X) but also a timeline: responses, another round of email messages, and a meeting by specified dates.