Before the digital era, he says more than 80 percent of business lines had voice mail. Now, he estimates only a third of office phones have it.”For customers, even the most professional voicemail greeting is impersonal, and may even harm customer experience (millennials, in particular, avoid using voicemail altogether).
YOD, or Bring Your Own Device, allows users to connect existing devices (smartphones, tablets, analog phones, desktop computers) to their virtual phone system, adding portability and eliminating the need to purchase an excessive amount of new equipment.

Common, but optional, equipment also includes headsets, speakers, analog phones, microphones, and even professionally installed conference rooms with things like digital whiteboard screens.
The Session Initiation Protocol (SIP) is one of the underlying technologies that make VoIP possible. This is a text-based protocol similar to HTML. It's the most commonly used standard for setting up and controlling phone calls in most VoIP systems. You'll run across references to SIP in almost anything you do with these kinds of phone systems, especially when you're selecting any handset hardware you want to use.