Absent subscriber: Absent subscriber due to the phone being switched off, due to phone out of coverage, due to roaming restriction/restricted area.
Absent subscriber (HLR Access Denied: Postponed): Subscriber cannot be reached at the time of broadcast or unknown subscriber. The Home Location Register is a database. It provides routing information for MT (Mobile Terminated) calls and SMS (Short Message Service) Absent subscriber (No acknowledgement): Absent subscriber due to the phone being switched off, due to phone out of coverage, due to roaming restriction/restricted area without acknowledgement.
Absent subscriber (Destination resource shortage): The message is rejected because there was no paging response, the IMSI record is marked detached, or the MS is subject to roaming restrictions.
Absent subscriber (SMS delivery postponed): User's mobile number not reachable or out of network coverage area.
Absent subscriber (Destination out of service): Mobile number barred at the carrier end.
Absent subscriber SM: Out of coverage area (or) switched off. The error might be due to the poor network coverage area and the same flag was updated in the HLR.
Note: Important Abbreviations:
| MT | Mobile Terminating | CUG | Closed User Group |
| MS | Mobile Subscriber | HLR | Home Location Register |
| SRI | Send Routing Information | VLR | Visitor Location Register |
| FSM | Forward Short Message | PDU | Protocol Data Unit |
| SGSN | Serving GPRS Support Node |