The destination number you are trying to reach is temporarily blocked from receiving this message.
This is because the SMS Pumping Protection feature has identified potential fraudulent messages being sent to the destination you are trying to reach.
A temporary block on SMS traffic has been placed for the next 15-30 mins on the phone number you used. This block will be lifted at the end of this 15-30 minutes period. If further fraudulent activity is detected after this block, this pattern will continue with temporary 15-30 minutes blocks until the issue is no longer observed.
You do not need to take any specific action. The disruption in traffic is usually temporary and will resolve in a couple of hours if we do not detect additional fraudulent activity.
Twilio's support team can help investigate what went wrong with delivering your message. Please collect 3 or more message SIDs in your SMS logs from the last 24 hours that were flagged with Error 30453, and open a support request.
Alternatively, you can use the optional RiskCheck parameter when creating a Message with the Programmable Messaging API. To prevent a known/legitimate message from getting blocked in future by SMS Pumping Protection, include the RiskCheck parameter with value disable when creating the new Message resource.
You can also mark known/legitimate phone numbers using the Global Safe List feature so that they don't face any disruption . This provides an additional safety net against false positives, so that the traffic to this number never faces the above scenario. Add known phone numbers to the Safe List by using the Global Safe List API.