1. An electronic message processing system arranged to receive electronic messages, the system comprising: means for storing a plurality of classification rules; at least one text analyzer; a respective rule engine associated with the at least one text analyzer and with the rule storage means, the at least one text analyzer and associated rule engine being co-operable to apply at least one classification rule to the content of a received electronic message and to generate at least one result based on the application of said at least one classification rule; a classification module co-operable with the at least one text analyzer and associated rule engine and arranged to classify the electronic message into at least one message category based on said at least one result, wherein the classification rules are arranged into a plurality of rule sets, said rule sets being associated with one another in accordance with a hierarchical structure, the classification module being arranged to cause the at least one text analyzer in association with the associated rule engine to apply at least one of said rule sets to the message content in accordance with said hierarchical structure wherein the at least one result generated by application of a rule set from said plurality of rule sets to the message content determines at least one other rule set from said plurality of rule sets next to be applied to said message content.
3. An electronic message processing system as claimed in claim 1 , wherein the a text analyzer includes the rule engine.