When a mobile device is powered down, it loses its connection to the cellular network. Consequently, any attempt to send an SMS message to that device results in the message being routed to the service provider’s Short Message Service Center (SMSC). The SMSC then stores the message temporarily.
The duration for which the SMSC retains the undelivered message varies depending on the carrier and network conditions. Typically, the SMSC attempts to deliver the message for a specified period, often ranging from a few hours to several days. This storage mechanism ensures that messages are not immediately lost when a phone is unavailable, enhancing the reliability of text communication.