Issue with SMS Delivery: Phone Carrier Blocking Messages

Question

Hello AWS Support,
We are experiencing issues with the SMS service using the sender ID we provided and that was approved by AWS. Despite the sender ID being enabled, our messages are failing to be delivered. Below is a summary of the failure details:
1. **Timestamp**: 2024-07-18 09:49:34.388
2. **Message ID**: 965e3e84-8e2f-5fbd-838b-619669415c35
3. **Phone Carrier**: Vodafone Essar - Maharashtra
4. **Delivery Status**: FAILURE
5. **Provider Response**: Phone carrier has blocked this message
6. **SMS Type**: Transactional

We have ensured that all required information and documents were provided during the sender ID registration process. The issue seems to be that the phone carrier is blocking the messages.
Could you please assist us in identifying the cause of this issue and provide guidance on how we can resolve it? We are keen to ensure our SMS services are fully operational and compliant with all necessary protocols.
For privacy reasons, I have omitted any sensitive details from this message. Please let me know if you require further information in a private manner.
Thank you for your assistance.

Makendran G · Answer

Hello Om Dhimar,

I would like to provide you with some background information on how SNS SMS works. When an SMS message is published to SNS, it is forwarded to downstream providers, who then forward it to mobile carriers, who finally send the message to the recipient's mobile phone. Mobile phone operators are responsible for the last leg of message delivery to phone numbers. The flow for SMS messages is as follows:

Client —> AWS (SNS) —> Downstream providers —> Phone carrier —> Endpoint (mobile device/recipient)

To send SMS messages to recipients in India, you need to provide the Entity ID and Template ID. These are defined as follows:

1. Entity ID – The entity ID or principal entity (PE) ID that you received from the regulatory body for sending SMS messages to recipients in India. 
2. Template ID – The template ID that you received from the regulatory body for sending SMS messages to recipients in India.

If you have missed the DLT details or provided incorrect information. then carrier will block the message. If you are correctly sending messages via the entity and template ID, Kindly check the message content as well whether you are sending the approved message content.

If you are using the AWS SDK, you need to use the AWS.MM.SMS.EntityId and AWS.MM.SMS.TemplateId attributes to send SMS messages.

For reference, please check the following documentation: https://docs.aws.amazon.com/sns/latest/dg/sms_publish-to-phone.html#sms_publish_sdk

If the above configurations are correct, please raise a AWS Support case with the message IDs to investigate further with downstream providers.

Issue with SMS Delivery: Phone Carrier Blocking Messages

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