SMS Delivery Failure


When you launch a marketing campaign or send an SMS, it is easy to take for granted that your text messages are delivered on time. But there can be numerous reasons why a message sent is not a message delivered. This article explains why your SMS is not delivered to the end-users and also gets to know the leading causes of why this happens.

This document is for the customers who are:

  • Launching the SMS Campaign for the first time
  • Looking out for reasons for SMS delivery failure

Below is the list of reasons why SMS may not be delivered to the end-user:

SMS Delivery Status

Table 1-1 displays the SMS delivery statuses and their descriptions:




Insufficient credits.


Mobile number series blocked.


Invalid number


Server error.


Spam SMS.


Sender ID not allocated.


Blacklisted number.


Template not mapped.


Template is not matching with the approved text.


Sender ID not found.


DND registered number.


Not subscribed for opt-in group.


Time out for promotional SMS.


SMS successfully delivered.


Number does not exist or fails to locate the number in the HLR database.


Telecom services are not providing service for the particular number or Mobile Subscriber not reachable.


Problem with the Handset:

  • Failed to get the complete message.
  • Does not support the incoming messages.


End user has enabled a message barring system. Subscriber only accepts messages from Closed User Group (CUG).


Subscriber’s operator not supported. Gateway mobile switching error.


Handset memory full.


SMS expired due to roaming limitations. Failed to process the message at operator level.


Mobile handset is in switched off mode.


Subscriber is in busy condition.


Series blocked by the operator.


SMS expired after multiple re-try.


SMS is rejected as the number is blacklisted by the operator.


Unsubscribed from the group.


Validation failed (SMS over 160 characters).


Failed due to network errors.


Operator has not acknowledged the status report of the SMS.

Incorrect Sender ID

A Sender ID is a set of alphanumeric characters that represent the identity of the sender. It is the name that appears in the From field when you send an SMS campaign. Also, an incorrect From field can be one of the reasons for SMS campaign failure.

By default, will create a Sender ID during the signup. However, using this default ID, you can only send SMS messages to your mobile number and the numbers that are added to the Team. Hence, you must create your own Sender ID to launch a global SMS campaign or send an SMS to other mobile numbers.



A-Team is a group created during your signup, allowing you to invite members and join your Team in the

The rules for creating a Sender ID may vary from county to county. For example, In India, you need to register the Sender ID with the network operator on the Distributed Ledger Technology (DLT) platform. Once registered, only then you can apply it in It is recommended to go through the global registration process before you create a Sender ID.

For more information on the Global Registration Process, refer to the below link:
For more information on Creating a Sender ID in the, refer to the below link:

Content Restrictions

Many countries enforce different types of content restrictions on network operators.
For example, in India, companies must register their Content and Consent Templates on the DLT. Japan does not allow you to add URLs in the message body.

For India specific information on the Content Registration process, refer to the below link:



Before you start an SMS campaign, we recommend you to research the content requirements of each destination country.

Time restriction on promotional SMS

SMS campaigns are one of the best ways to promote your products. However, there are time restrictions enforced by various countries.

For example, in India, if you run a campaign outside the permitted hours of 9:00 PM to 9:00 AM then, the SMS campaign shows as failed or message undelivered.



Before you start an SMS campaign, we recommend you to research the time restrictions for each destination country.

Country Code not entered

Before sending an SMS to the contacts, ensure to prefix the country code to the mobile number. Else, the system will consider the first two digits of the mobile number as the country code, which results in the SMS campaign failure.

Incorrect Country Code

Ensure the country code entered is correct when you are sending SMS to multiple countries.

Other reasons for SMS Campaign Failure

Below are some of the other reasons:

  • Exception Time Out
  • Message Inbox memory is full on your mobile device (Lack of space in the receiver's Mobile internal memory for new messages).
  • The number is out of reach (not reachable or out of coverage area).
  • Handset failure(The receiver handset is damaged or is not working properly).
  • Network failure (The carrier network is facing some technical difficulties and messages are just not able to be delivered. (Downtime caused by network problems, Security failure, Hardware failure, etc.).



Kalyera's system is configured to retry the delivery of messages within a few hours. If the message still fails, it is marked as Failed.

If you are still not able to resolve the issue, contact our support team at [email protected].

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