Incident notice:
what went wrong, and what we fixed

Published 24 September 2026 · HantarSMS

What happened

Starting on the evening of 21 September, the connection between our platform and the carrier gateway became intermittently unstable on the carrier side. A small share of submissions were returned with a connection error (HTTP 522/525) before the message ever reached the carrier.

Two things in our system then went wrong, one after the other:

• We treated those connection errors as result unknown, possibly sent, and did not retry. In fact those messages had definitely not been sent.
• When checking delivery for those messages, our matching logic could pick up the delivery receipt of a different message to the same number sent shortly before, so the report showed Delivered for a message that never went out.

We found it on 24 September when one of our own test messages showed as delivered and was never received.

Who was affected

Ten messages across three customer accounts, plus two of our own test messages. Every one of them was a single message or part of a campaign; no campaign was affected as a whole. If you were affected, the credit for those messages has already been returned to your balance, and the entry in your Send history now shows the true status (Send failed, with the reason). You do not need to do anything.

Messages that got a genuine delivered receipt from the carrier were correct throughout. This incident only concerns messages that never reached the carrier.

What we changed (live since 24 September)

• Connection errors are now retried, never charged as "unknown". When the carrier gateway cannot be reached (522/523/525/526), the message is retried automatically and, if it still cannot be sent, refunded. It is never marked as sent.
• Nothing is reported as delivered without evidence for that specific message. A message with no carrier transaction ID can no longer borrow the receipt of another message to the same number, and is never presumed delivered by timeout. It shows as Not delivered until we have a real receipt for it.
• A daily test message. Every day at 10:00 a real message goes from our own account to two real phones through exactly the same path your messages take. If it is not received, we know before you do.
• We reviewed every message from the last 30 days with the same failure signature and corrected the report and the balance for each one.

What you can check

Open Send history and look at 21–24 September. Any message that was affected now shows Send failed with a note that it never reached the carrier, and the matching refund appears in your top-up history. If anything looks wrong to you, message us on WhatsApp with the campaign number and we will go through it with you.

We built HantarSMS on the promise that the delivery report shows what really happened. For a few days it did not, and we are sorry. The fixes above are in place so that this particular failure cannot repeat silently.