The Short Message Service Centre (SMSC) is an element in a GSM network responsible for the delivery of short messages (SMS). All messages are sent to the SMSC. The SMSC stores the messages, extracts the destination from it and tries to deliver the message. If the message can not be delivered, the SMSC will try again to deliver the message in a so-called retry-schedule. If the mobile phone is turned on or comes within reach of the network, the SMSC will also retry to deliver the message. If a mobile telephone received a message, it will send an acknowledgement back. Usually the message will be discarded after two days if the destination can not be reached.
The number of the SMSC has to be programmed in the mobile phone.