Incident Description: An issue was reported regarding SMS Delivery Receipts (DLR) returning Error 200 with messages remaining stuck in a "Submitted DLR" status via API. Investigation and resolution required addressing multiple layers across API integration, network security, Cloudflare configurations, and telco route performance. Attach Image (Optional):

Business Impact: End-User Deliverability Drop: Non-delivery of messages to invalid, inactive, or network-blocked destination numbers resulted in downstream delivery failures and elevated error rates (Error 8 / Network Blocked). Resource Waste on Invalid Traffic: Inactive and unknown subscriber destinations consumed network request attempts before traffic scrubbing and route optimization were implemented.

Corrective Actions Taken: -Guide the API integrator to use Alias Message ID on API. -Whitelisted the correct IP addresses. -Resolve the corrupt Cloudflare Browser integrity check. -Determine which route is unreliable and reroute to the tested network.

Additional Information: Several issues resolved -Alias Message ID API requirement. -Application IP was not whitelisted. -Issue on Cloudflare Browser integrity check. -API integration was prioritized before SMS traffic issue. -Mobile numbers are found to be inactive, unknown subscriber, and blocked. -The user application is now routed to the tested network. Attach Image (Optional):