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Most common reasons of SMS delivery failure

Updated

This article describes the most common reasons why your SMS was not delivered to the customer and provides troubleshooting steps for initial investigation.

 

1. Lacking phone number and SMS consent

Issue: The phone attribute in the customer's profile is empty or not formatted correctly. The customer has not opted in or has opted out of receiving messages.

Troubleshooting tips: 

  • Check the "phone" attribute in a customer's profile. The attribute must not be empty and has to follow one of the formats:

                  With "+" and Country Code: +441234556789

                  Without "+": 44123456789

  • Find the SMS consent in the "Consents" tab of the customer's profile. A valid consent will have a green checkmark. If the consent is not granted, a red cross will appear near it.

Tip: If the "phone" attribute does not currently follow one of the correct formats in your project, check out this guide - How to convert format of phone number to string and add "+" in the beginning of the attribute – Help Center

2. Device switched off

Issue: If the recipient's device is switched off or has a poor signal, the SMS cannot be delivered. 

Troubleshooting tips:

  • When the recipient's device is switched off or out of network coverage, the systems will try to resend an SMS within the 48-hour window. During this time, the service provider will make multiple delivery attempts before marking the SMS as undeliverable if it still fails to reach the recipient's device. The returned failed delivery event will typically include an error message or code. 

3. SMS returned with an error code

Issue: SMS campaign event (or mapped event) with status "rejected" or "failed."

Troubleshooting tips:

  • If you notice an SMS issue with one specific customer, check the failed SMS campaign event (campaign - action_type -  sms) in that customer's profile. Look for event properties like "status_code", "error", "comment".
  • If you are having issue with an SMS campaign deliverability, create a report that will return the number of failed SMS campaigns with respective status or error codes. Here is an example of a report:
  • Once you see the most common error(s) for your campaign, you can find out what they mean based on the SMS integration used. Typically, it is one of the three: 

    Infobip
    Delivery report error codes
    SMPP error codes
    Delivery report statuses

    Sinch
    Delivery report error codes
    SMPP error codes

    Twilio
    Error and Warning Dictionary
     
  • Check error codes against the list from your provider to find out more about the reason of failed delivery.

4. Non-compliance with local regulations

Issue: Failure to comply with the local regulations can result in penalties, blocking of sender IDs, and legal challenges, and may ultimately affect deliverability and the reputation of the brand.

Troubleshooting tips:

  • Make sure you send the messages only to contracted countries.
  • When you want to use SMS as a marketing channel in the US, you must first comply with the Telephone Consumer Protection Act (TCPA).
  • Use a correctly registered sender name since it adheres to regional requirements.
  • Before sending SMS campaigns, get to know the regulations of the countries you will be sending them to.

 

 

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