58. The apparatus in claim 52 wherein the classes comprise a plurality of sub-classes and said one class is one of said sub-classes.
52. The apparatus in claim 37 further comprises a training phase wherein the processor, in response to the stored instructions: detects whether each one of a plurality of predetermined features exists in each message of a training set of m messages belonging to the first class so as to yield a feature matrix containing feature data for all of the training messages, wherein the plurality of predetermined features defines a predefined n-element feature space and each of the training messages has been previously classified as belonging to the first class; reduces the feature matrix in size to yield a reduced feature matrix having said N features (where n, N and m are integers with n&gt;N); and applies the reduced feature matrix and the known classifications of each of said training messages to the classifier and training the classifier to recognize the N features in the m-message training set.