AWS SNS (Simple Notification Service) not sending transactional messages consistently.


The SNS service not sending the messages consistently. For the same mobile number, getting "Phone carrier has blocked this message", after 1-2 retries the message is sent to the same number. SNS region: ap-southeast-1 (Singapore) Message had OTP for user confirmation. The user mobile number is from India.

1 Answer
Accepted Answer


Short answer: we now have a Messaging blog that describes possible reasons to SMS failures .

Long answer, is described below:

Let's first take a step back and understand Amazon SNS/Pinpoint SMS workflow as summarized below :

SNS --> Downstream providers --> Mobile Carriers --> Device

When an SMS is sent using AWS services (e.g. SNS or Pinpoint), its forwarded to Downstream providers who route the SMS to mobile carrier. The mobile carriers are responsible for the final delivery of the SMS message to end-user phone device. Different destination country have different local laws and regulations to which SMS sender should comply to. For example, sending unregistered SMS to India using SenderID will fail, sending URLs as a part of SMS might fail for Nordic destinations.

In the context of the message - Phone carrier has blocked this message, this means that there a high probable cause of delivery issue between Downstream providers process to mobile devices hence SMS was not delivered successfully.


Please strongly encourage our customers to contact AWS Premium Support and provide the following additional details needed for further investigation:

AWS Account ID

AWS region

3 - 4 SNS SMS logs (i.e. not older than 72 hours)

Lastly I enlist SMS best practices for further reading and review.

answered 2 years ago

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