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SMS Message Expiry – A Guide

What is SMS message expiry?

If any text message cannot be delivered to its intended recipient immediately, their mobile network will attempt to re-deliver it over a period of hours or days, up until a designated ‘expiry’ time.

The precise time varies from one network to another, so there’s no standard validity period

After this time, if the message cannot be delivered, it will be discarded by the network and marked with a status of ‘EXPIRED’.

What are the common reasons that a text message expires?

There are a few reasons why an SMS might expire and not be delivered

  1. The phone is switched off for an extended period, usually over 48 hours. After this time the network operator will no longer attempt message delivery and it will be marked as expired.
  2. The phone is in a very low mobile signal area for an extended period. This seems an unlikely outcome in 2023 but there are still some rural areas in the UK that have very patchy mobile signal.
  3. The phone is ‘hanging’ on the network. Occasionally a phone will appear to be connected to the network, with the mobile strength indicator showing good mobile signal strength.

    The phone is however not correctly connected and text messages are unable to be delivered.
    The solution to this is to simply reboot the mobile and force a network reconnection.

  4. Mobile phone is in airplane mode. This normally happens if a traveller forgets to switch off airplane mode after a flight.

Mobile phone

How do I prevent messages from expiring?

Two circumstances can prevent message expiry. Firstly, and obviously, the message can be delivered. Secondly, a ‘permanent’ error can occur. 

Permanent errors describe circumstances under which the message will definitely not be delivered, regardless of the number of repeated attempts to deliver the message within the expiry period.

What is the default expiry time?

The default expiry period varies, depending on the SMS provider. The SMS Works sets the default expiry period for messages sent from its platform at 48 hours. 

Can I change the expiry time for an SMS?

You may not want to wait for the default expiry period to pass before taking some alternative action.

Most providers let you set the expiry period for the SMS messages that you send through them.

The SMS Works Message API allows you to specify a ‘validity’, in minutes, after which the mobile network will return an EXPIRED status if the message cannot be delivered and no permanent error has occurred.

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Phil Warner Technical Director
Co-founder and Director of The SMS Works, a low cost and powerful SMS API for developers. About Phil.