To provide a mail tracking system allowing a user asking mail enclosing an RFID tag to be sent to retrieve tracking information of the mail through a network.

This mail tracking system is composed of undertake stations A1, B2, C3 undertaking mail from senders a to f and DM companies A to C, a relay station 4 assigning the mail at the undertake stations A1, B2, C3 to each delivery station, delivery stations A10, B11, C12 delivering the mail from the relay station 4 to receivers (a) to (f), the network 5 transmitting information of each station to a central station 6, and the central station 6 putting information of each station together through the network 5. Each constituent element is connected with the network 5.