When you think of SMS messaging, typically people refer to messaging via mobile phones through Mobile Network Operators (MNOs).  Over the past few years, we’ve seen the rise of the so-called NUVOs – Network Unaffiliated Virtual Operator – a type of OTT service provider who offers phone number based and app-based messaging on smart devices that also interworks with the existing SMS ecosystem. This means that a NUVO subscriber can send and receive messages from an AT&T or a T-Mobile or Verizon subscriber.