There can be different reasons for nondelivery of an SMS such as exception time out, message inbox full or if the number is out of reach.
These are the basic reasons for the failure of an SMS:
- Number out of coverage area/ Switched Off / TEMPORARILY UNAVAILABLE.
- The recipient cannot receive incoming messages.
- SYSTEM FAILURE– Network or Protocol Failure other than the listed. The task cannot be performed because of a problem in another entity. The type of entity or network resource may be indicated by a network resource.
- SMS timeout after all retry
- Network failed
- Unidentified Subscriber, No response from the handset
- Subscriber is not available at that time
- Inbox memory is full or exceeded
- INBOX FULL– Short Message rejected by MS because of no memory capacity to store the messages.
- Congestion Encountered at the visited MSC or the SGSN.
- Recipient MS has no SMS subscription.
- UNKNOWN SUBSCRIBER– No allocated IMSI or directory number for the mobile subscriber in the HLR.
- ILLEGAL SUBSCRIBER– The PLMN has rejected the short message because the MS failed authentication.
- EXPIRED MAXIMUM RETRIES EXCEEDED– All the retries from different operators have been made.
- SM DELIVERY FAILURE– It can be due to below mentioned reasons,
- Unknown Service Center Address.
- Service center congestion.
- Invalid short message entity address.
