Sinch messaging integration: design for consent and carrier outcomes

Provider acceptance is not final delivery, and messaging rules vary by channel and country.

• Record opt-in source and process opt-outs immediately.
• Normalize destinations while retaining country context.
• Make sends and webhook handling idempotent.
• Store event and receipt times separately.
• Bound fallback across SMS, MMS, and app channels.

Test invalid numbers, carrier filtering, template failure, delayed receipts, segmentation, and regional sender restrictions. Minimize message and recipient data in logs.