How do I troubleshoot SMS delivery delays in Amazon SNS?

Short description

SMS delivery might delay for the following reasons:

• The recipient's device experienced technical issues such as storage limitation and low signal strength.
• The phone number is temporarily out of the coverage area.
• The phone number is in a roaming network.
• There's increased network traffic for a particular carrier.
• A carrier tried to deliver the message when the device was turned off.

Resolution

Follow these troubleshooting steps for your use case.

Troubleshoot single device issues

1. Restart the device so that it's connected to the nearest network base station.
2. Change the SIM slot to check for a device issue.
3. Check the devices message storage, and then delete messages that you don't need.
4. Make sure that the device can receive SMS messages from other sources.

Troubleshoot multiple device issues

If delayed SMS delivery affects multiple devices, then there might be issues with downstream providers and carriers.

To troubleshoot potential downstream issues, create a support case for Amazon SNS. Provide the following information in your support case:

• The AWS Region that you use to send SMS messages.
• A timestamp of when the issue started.
• Three samples of SMS logs with the message IDs of failed SMS messages to different phone numbers not older than three days.

Note: Mobile carriers might not store SMS information for more than three days.

CloudWatch Logs

If you use Amazon CloudWatch Logs to monitor your SMS message deliveries, then the SMS delivery times might not be accurate. Amazon SNS might deliver SMS messages before CloudWatch receives the logs. The dwellTimeMsUntilDeviceAck value in the delivery logs shows when the carrier accepted the message, but doesn't provide information on delayed SMS messages. For more information, see Amazon SNS SMS delivery monitoring with Amazon CloudWatch metrics and logs.

Related information

Monitoring Amazon SNS topics with CloudWatch