Post-Mortem: SMS Delivery Incident - 25 June 2026
Following the resolution of this incident, we want to provide a fuller post-mortem for transparency.
What happened
As our SMS provider has continued their investigation, it has been determined that a component within their messaging platform responsible for routing outbound messages stopped working. This was a widespread event.
As a result, messages were not processed as expected, and a backlog built up. They then stopped accepting new messages from platforms like Zanda. The SMS provider was not able to directly fix the impacted components, so they provisioned new infrastructure. Outbound messages were then routed via this infrastructure. They then started accepting messages again, and message sending resumed as normal.
What we did
We received some initial reports from customers stating that SMS messages had not been received by clients. We commenced an investigation immediately, which identified that SMS messages from Zanda were being sent to our SMS provider correctly, but that they were experiencing a processing issue, as described above.
On our end, we were able to identify new messages that were not being accepted by the SMS provider. We then flagged these, requeued them, and sent them once the SMS provider had provisioned the new infrastructure.
We were also in contact with the SMS provider during this time and received updates as they worked through the issue. We also posted a notice in Helperbee and commenced this incident page so all Zanda customers could be kept up to date as the situation unfolded.
Impact
The vast majority of SMS messages sent on 25 June were delivered correctly and on time. During the affected period, SMS messages were sent, but after a delay of anywhere from a few minutes to several hours.
Our initial understanding was that all SMS messages received by our SMS provider were sent. However, they are still reconciling their SMS logs. We have been advised that some SMS messages may have been delivered multiple times, and that some messages (sent during the earlier phases of the incident) may not have been sent at all.
We sincerely apologise for the disruption this may have caused.
What we’re doing
As our SMS provider continues its reconciliation of SMS messages, we will be applying credits for any SMS messages that were not delivered, as well as ensuring that there were no charges incurred where SMS messages were sent multiple times.
While we have confidence that our SMS provider understands the significance of an incident like this, we are also ensuring that they are fully aware of the impact this had on Zanda’s customers and their clients.
We take the reliability of our platform seriously and will continue to monitor our SMS delivery closely going forward.
Thank you for your patience and understanding throughout this incident.
