A2P SMS Delivery Status & Error Code Meaning in Bangladesh Operator Networks

Introduction

For A2P SMS delivery, an SMS passes through multiple network elements including SMS Gateway, SMSC, SS7/MAP signaling, HLR, MSC, and the subscriber handset.

The Delivery Report (DLR) received from an operator/IPTSP contains an error code that indicates the final status of the SMS transaction.

This document explains common operator error codes and their meaning for Bangladesh SMS traffic.

SMS Delivery Status Mapping

Error Code	Error Name	Meaning / Description	Retry Policy	MiMSMS Standard Status
0	Delivered	SMS successfully delivered to the subscriber handset	No Retry	DELIVERED
6	Absent Subscriber for SM	Subscriber is not reachable. Mobile may be switched off, out of coverage, or not registered on network. Usually temporary condition.	Retry 3 Times	UNDELIVERED
32	Undelivered	Subscriber handset cannot receive SMS due to insufficient message storage/memory capacity.	No Retry	UNDELIVERED
31	Subscriber Busy	MSC is busy processing another transaction. Subscriber may be receiving SMS or network transaction is ongoing.	Retry 3 Times	PENDING
5	Unidentified Subscriber	MT number is unknown in the MT network MSC. Subscriber record not found in operator network.	No Retry	UNKNOWN
13	Barred Subscriber	Subscriber is not allowed to receive SMS. Possible reasons: unpaid service, operator restriction, blacklist, or user-requested blocking.	No Retry	REJECTED
9	Illegal Subscriber	SMS rejected because sender ID/content/traffic pattern is blocked by operator policy for illegal or unauthorized SMS traffic.	No Retry	REJECTED
36	SMS Failed	SMS rejected due to operator sender ID/content filtering or traffic restriction.	No Retry	UNKNOWN
34	System Failure	Failure caused by SS7/MAP signaling issue or operator network system problem.	Retry 3 Times	FAILED
8	SMS Failed	SMSC link/network communication failure between SMS systems.	Retry 3 Times	FAILED
400 / 456	SMSC Timeout / Abort	SMSC did not respond within expected time. Transaction expired due to timeout.	Retry 3 Times	EXPIRED

Detailed Explanation of Important Errors

1. MT Number Unknown (Error Code: 5)

Meaning:

The destination MSISDN is unknown in the operator’s MT network MSC.

Common Reasons:

• Number is inactive
• SIM permanently disconnected
• Wrong MSISDN format
• Incorrect MNO routing
• MNP routing mismatch

Example:

SMSC → HLR Lookup → MSC
              |
              └── Subscriber Not Found

Recommended Action:

• Validate MSISDN
• Check operator routing
• Verify number status

2. Absent Subscriber (Error Code: 6)

Meaning:

The subscriber exists but cannot currently receive SMS.

Common causes:

• Mobile switched off
• Out of coverage
• Temporary network unavailability

Recommended Action:
Allow operator retry mechanism.

3. Barred Subscriber (Error Code: 13)

Meaning:

Operator has restricted SMS delivery to the subscriber.

Possible causes:

• Subscriber account restriction
• Regulatory blocking
• User requested SMS blocking
• Operator blacklist

4. Illegal SMS Traffic Block (Error Code: 9)

Meaning:

Operator blocked the SMS due to policy violation.

Common causes:

• Unauthorized sender ID
• Unregistered brand name
• Suspicious content
• Promotional traffic violation

Best Practice:

Always include brand identity:

Example:

“Your login OTP is 123456. Valid for 5 minutes. Do not share this code. (MiMSMS)”

5. System Failure (Error Code: 34)

Meaning:

The SMS failed because of network/system communication failure.

Possible causes:

• SS7 signaling issue
• MAP transaction failure
• Operator core network issue

Recommended Action:
Retry submission.

Recommended Retry Strategy

Error Category	Retry Recommended
Temporary Network Issue	Yes
Subscriber Busy	Yes
Absent Subscriber	Yes
Invalid Number	No
Barred Subscriber	No
Unknown Subscriber	No
Illegal Traffic Block	No

MiMSMS DLR Status Standardization

To provide a simple reporting format, operator-specific error codes are normalized into:

Standard Status	Meaning
DELIVERED	Successfully delivered
PENDING	Temporary condition, retry expected
UNDELIVERED	Subscriber/device unavailable
UNKNOWN	Subscriber status cannot be determined
REJECTED	Operator or subscriber restriction
FAILED	Technical/network failure
EXPIRED	Delivery window exceeded

Conclusion

Operator DLR codes help identify whether an SMS failure is caused by subscriber availability, routing, content filtering, or network problems.

For A2P SMS troubleshooting, always analyze:

• DLR Error Code
• Destination MSISDN
• Timestamp
• Operator route
• Sender ID
• Message content

This helps MiMSMS and partners quickly identify delivery issues and improve SMS success rates.