What happens if I send an SMS to a phone that has poor signal or is turned off?

Using the engageSPARK platform is incredibly easy! We have many features that allow you to see the status of the different SMS being sent. You can see if an SMS was sent, delivered, or failed. While SMS is a very reliable way of communication, sometimes SMS can fail to reach your contact’s phone for various reasons.

Here we will explain what happens when you send a SMS to a person without a phone signal or who has a very unstable phone signal or who simply has their phone switched off.

What happens?

If the recipient’s phone is turned off or has a very unstable/poor signal, the SMS might not get delivered to the phone on the first try. The mobile network operator (MNO) will keep trying to deliver the message to the recipient. Different MNOs have different retry mechanisms. Typically they try to resend the messages within 24 hours. The retry timeframes vary and depend on three factors: country, MNO, and messages in the MNO’s queue.

For example, if the MNO only has a couple of dozen messages that need to be resent, the timeframe will be shorter because the frequency in which they are trying to re-send the SMS is faster. If there are hundreds or thousands of messages that need to be resent (maybe due to a massive signal disruption), then the frequency of retries will be lower since the MNO’s queue is bigger. Hence, longer timeframe.

What happens to the messages not sent?

Once a message fails to be delivered and the re-try period has expired, that message is simply lost. If you wanted to get the same message out again, you would have to write a new SMS with the same content or re-subscribe the phone numbers that failed to your engageSPARK campaign.

If a message has expired, on some SMS (depending on the country and MNO) you will be able to see the status “failed” in the engageSPARK downloadable campaign report. For the delivery statuses in the campaign report, we rely on what is called “Delivery Receipts” (DLR) which are a kind of report that is given back to us by the different MNOs. Not all MNOs support DLRs and these can be inaccurate from time to time. For those MNOs that do not support DLRs, you might see the status of your SMS as “sent” instead of “failed”. When this happens you can let our team know and we will investigate what has happened with the SMS.

All SMS that are sent out will be charged their corresponding cost regardless of outcome and status.