A Short Message Service Center (SMSC) is a network element in the cellular phone network. It stores, forwards, converts and delivers the SMS messages.
The full description of an SMSC according to 3GPP is Short Message Service - Service Centre (SMS-SC)
Guaranteed delivery: if a wireless recipient is switched off, out of range or if there is a network outage, the SMS message will be stored in the network and delivered when the recipient announces its presence, or when the outage is rectified. This is the basis of the store-and-forward concept.
An SMS center (SMSC) is accountable for managing the SMS operations of a wireless network.
An SMS message is stored temporarily in the SMS center if the recipient mobile phone is unavailable. Expiry period of a SMS is 24 hours after which the SMS message will be deleted from the SMS center.
Detailed report is provided by the technical team to the clients regarding the number of stored, delivered and recipient's details.