The type distinguishes between traditional ezines, mailing lists, and discussion lists. The central feature of all of these types of communication is that they take place via email. Usenet and weblog discussion groups won't be listed on The Ezine Machine. The type field is required.

A "traditional" ezine is completely owned by a single editor, who decides all major editorial policies, such as content and frequency. Nobody but the editor can send out an ezine, and generally the subscribers don't know each other, and don't have access to the email addresses of other subscribers.

A mailing list is a less formal arrangement than an ezine. Typically, items going to a mailing list appear on an irregular schedule, depending on the requirements of the owners of the list. Also, members of a mailing list can typically discover the other members of the list simply by reading the headers of email they receive.

A discussion list is even less formal - any member of a discussion list can originate a message to the list, and the members of a discussion list almost always know each other.