A relay apparatus for transferring message data received from a client to one of a plurality of servers includes a status management data storage, a transfer rule handling section, and an acknowledgment transmitting section. The status management data storage holds data of an acknowledgment necessity table. The acknowledgment necessity table includes first identification information of a first apparatus to which the relay apparatus acknowledges when the relay apparatus has received first transfer rule notification data from the first apparatus. The transfer rule handling section determines whether the acknowledgment necessity table includes the first identification information identical to second identification information of a second apparatus upon receiving second transfer rule notification data from the second apparatus. The acknowledgment transmitting section transmits acknowledgment data to the second apparatus when the acknowledgment necessity table includes the first identification information identical to the second identification information.