What are the reasons behind a failed message?

There can be different reasons for the failure 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:

• EXP Abssubs - Subscriber is not available at that time 
  
  
• EXP Memexcd - Inbox memory is full or exceeded 
  
  
• EXP Smstmout - SMS timeout after all retry
  
  
• EXP Nwfail - Network failed
  
  
• Resource Unavailable- The message was aborted by a network peer because of a network protocol error. 
  
  
• ABSENT SUBSCRIBER- Unidentified subscriber, No response from the handset
  
  
• NUMBER TEMPORARILY UNAVAILABLE- Number out of coverage area/ Switched off
  
  
• CALL BARRED- 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.
  
  
• HLR/ MSC Timeout- If HLR (Home Location Register) does not get the response from the MSC (Mobile Switching Centre) then there will be a timeout
  
  
• INBOX CAPACITY EXCEEDED- Short message rejected by MS because of no memory capacity to store the messages
  
  
• SUBSCRIBER BUSY FOR MT SMS- Congestion encountered at the visited MSC or the SGSN
  
  
• TELESERVICE NOT PROVISIONED- Recipient MS has no SMS subscription.
  
  
• Services temporarily blocked- Terminated due to mobile subscriber operator (services blocked by the network operator)
• Message Service Not Supported: This indicates that the mobile subscription associated with this number does not support the short message service (SMS). This means that the requested service, such as SMS, is unavailable or has not been activated for the subscriber's account. Resolving this error usually involves contacting the service provider or network operator to ensure the teleservice is provisioned and activated for the subscriber's account.
• UNKNOWN SUBSCRIBER- No allocated IMSI or directory number for the mobile subscriber in the HLR
  
  
• ILEGAL 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
  
  5303- Header not associated with this template
  5304- Template ID not found on DLT
  5307- SMS not Matched with DLT Template
  
  
• SM DELIVERY FAILURE- It can be due to the below-mentioned reasons,
  
  

1. Unknown Service Center Address
2. Service center congestion
3. Invalid short message entity address
   
   

• Failed - No specific reason found for non-delivery (after certain attempts by multiple operators)
  
  
• Rejected by Provider - The SMS was rejected by the provider due to the promotional content through the transactional route
  
  
• Equipment Protocol Error - This is a temporary error related to the handset, specifically tied to temporary issues that can be resolved by restarting the device or reinserting the SIM card.