E-Mail games that don't really qualify as regular games with a concrete set of rules and a clear objective. The rules and objective may change, part of the game may be discovering the rules and objective, or it just may be something closer to entertainment then a regular game.
Nomic played entirely through a web site (no e-mail lists required) go in Games: Internet: Web: Nomic.
A Nomic is a game where one of the objectives, and at the beginning the only one, is changing the rules. The initial rules consist of little more than describing how to change them. They can grow, morph, shrink, and do just about anything that the players want. This category covers web sites dedicated to Nomics played over e-mail.
Nomic played entirely through a web site (no e-mail lists required) go in Games: Internet: Web: Nomic.