Universal message delivery system

A message delivery system, for use with a communication network and in which a network presence is provided for an entity having attributes, delivers a message from a sender to the network presence. In some cases, information identifying the sender is omitted from the message. The delivery system can append non-repudiable sender information to the message. The sender can provide selected attributes as an address, and the delivery system replaces the selected attributes with an address of the network presence without disclosing the address to the sender. A software agent processes the delivered message in accordance with a processing preference included in the entity attributes.