There are now hundreds of thousands of e-mail discussion groups ranging in size from a few dozen to tens of thousands of members. One simple method is simply to advertise on the list.
Many discussion lists accept paid advertising.
Your text ad will appear one or more times in the body of the digest for that day or that week, usually emphasized by a decorative border. However, an even more effective way of using e-mail discussion lists is to participate in them yourself. This offers the added advantage of not costing any money. You will, however, need to invest time and effort into crafting a message that adds value to the discussion. Remember that a discussion list might give you access to a targeted group of prospects for your product or service, but that is not its purpose.