Understanding SMS Delivery

This section presents some information about SMS delivery, including but not limited to the different message states and their meaning, the reasons for the non-delivery of SMS, and some advice on how to improve deliverability.

Understanding Message States

Every SMS message request has a status value which describes the current state of the message.

  1. Intermediate states reflect a status when a message is processed by the Unifonic platform.
  2. Final states reflect the delivery status after a message was submitted to the mobile operator.

The Intermediate Message States

Message StateDescription
Queued The message has successfully passed the validations and then queued for delivery to the mobile operator.
Sent The message is successfully submitted to the mobile operator. The state of this message typically will be replaced by either Delivered or Undelivered within seconds or minutes according to the delivery confirmation received from the mobile operator.

The Final Message States

Message StateDescription
Delivered Unifonic has received confirmation of message delivery from the mobile operator or where available - from the destination mobile device.
Undelivered The message has NOT been delivered to the mobile device, for one of the following reasons:

– The message has not passed validations within Unifonic platform.
– Unifonic has successfully submitted the message to the mobile operator but received a delivery receipt indicating that the message was not delivered to the mobile device.

See Understanding Reasons of Non-delivery for a detailed explanation of why a message might have not been delivered.
Delivery not confirmed Unifonic has successfully submitted the message to the mobile operator, but neither received a confirmation of successful delivery nor an indication of non-delivery. This may happen because of the various reasons such as mobile operator settings blocking delivery receipts and connectivity glitches.
Normally the user wouldn't see many messages with this status, but if you do - please contact Unifonic customer support to investigate with the mobile operator.

Delivery Monitoring

There are two ways of monitoring the delivery of SMS messages on the Unifonic platform:

  • Real-time Message Logs
  • Delivery Status via Webhook
  • The first method enables the user to monitor message deliverability in real-time via the Unifonic Console.


For more information on accessing the Message Logs refer to Real-time Message Logs Report.

  • The second method is based on setting up a webhook for receiving delivery status that enables the customer to take actions programmatically on certain conditions (e.g. when deliverability drops below a certain threshold).


For more information on setting up the webhook refer to – Receiving Delivery Status via Webhook.

How To Improve Deliverability

Deliverability is the percentage of messages that reach the intended recipient and it’s one of the most important criteria when deciding on an SMS provider either for marketing campaigns or for transactional message delivery such as one-time passcode. There are a few best practices to improve the likelihood of the message being delivered to the recipient.

  • Make sure the recipient's phone number is correct. Regularly clean your customer phone number database to make sure each SMS recipient's phone number contains valid country code (such as 971 for UAE), operator prefix and the correct number of digits. Unifonic will be performing phone number validations based on the operator prefix and the number length. If the number is wrong then the message will not be delivered.
  • Craft the message to avoid filtering. Filtering is when a mobile operator blocks messages from going through because the content within that message is believed to be against acceptable use policies or regulatory rules (e.g. contains profanity language, phishing or SPAM). If you have to use URL in your message make sure to avoid using public link shorteners such as Bitly or TinyURL – please use your branded URL or Unifonic Link Shortening.
  • Validate API request before sending production traffic. Make one or two requests before sending a production traffic over API to make sure all parameters are included, you receive 200 OK response from the Unifonic API and message is actually delivered on the mobile device.

What’s Next