ActiveDEMAND is a platform designed to do campaign emails. Thus the typical way is to create a campaign and use a list. That being said, ActiveDEMAND has a great outlook plugin and a Chrome extension that allows salespeople to send one off tracked emails using ActiveDEMAND. If you are using Outlook or Gmail, you can use templates that include the ActiveDEMAND dynamic fields.
Here is a short video showing you how to make email templates using Gmail.