1. A message switching apparatus, comprising: message receiving means for receiving a particular message and a destination address of a receiver of the particular message from a sender operating a sender's communication terminal or information terminal; motive-procedure set storing means for storing a plurality of motive-procedure sets, each motive-procedure set being composed of a motive and a message processing procedure with condition, the motive being expressed by an event, the event determining a start of an operation of one message processing procedure with condition corresponding to the motive, the occurrence of the event being expressed by the firing of the motive, the message processing procedure with condition being composed of both a message processing procedure and a condition of the performance of the message processing procedure, and the message processing procedure indicating a procedure of a processing performed for a message; motive firing judging means for identifying the receiver according to the particular message received by the message receiving means, retrieving a plurality of specific motive-procedure sets corresponding to the receiver from the motive-procedure set storing means, identifying a plurality of specific motives corresponding to the specific motive-procedure sets, detecting the occurrence of a particular event expressing a particular motive among the specific motives, selecting a particular motive-procedure set corresponding to the particular motive from the plurality of specific motive-procedure sets, and judging the firing of the particular motive; message processing procedure performing means for performing a particular message processing procedure with condition of the particular motive-procedure set in cases where it is judged by the motive firing judging means that the particular motive is fired and a particular condition of the particular message processing procedure with condition is satisfied; and message transmitting means for receiving the particular message and the destination address of the receiver from the message receiving means, transmitting the particular message to a receiver's communication terminal or information terminal indicated by the destination address of the receiver in cases where a particular message processing performed by the message processing procedure performing means indicates the transmission of the particular message to the receiver.