For more than three decades, SMS has been the backbone of mobile communication. From the first “Merry Christmas” text in 1992 to today’s enterprise-scale messaging campaigns, traditional telco messaging has proved remarkably resilient. Yet the past decade has witnessed the meteoric rise of Over-The-Top (OTT) applications —WhatsApp, Viber, Telegram, WeChat, and many others — that bypass telco infrastructure, offering richer, app-based messaging experiences.