1. A method for classifying email messages, the method comprising using a plurality of modules to determine a level of sameness of a particular email message with one or more prior email messages, wherein the level of sameness is derived for the particular email message from a weighting of the outputs of the modules; determining a performance level for each of the modules; comparing performance levels; adjusting a weighting of at least one module in response to comparing performance levels; and using the level of sameness for the particular email message to classify the particular email message into a category.