People around us can need help at any time of the day. Many a time friends, family, boss, colleagues, relatives, and acquaintances need to inform us of something important at odd hours. Some may know when to call you and some of them won’t. In cases where you are not accessible, leaving a simple voicemail on your phone can ease their worry.
The basic rule of thumb is that callers should hear one of two things when they first connect with your voicemail — either an apology for not being able to answer the call or a “thank you” for having called. You can do both if you prefer, but keep it short and to the point.

This feature mimics an answering machine. Five seconds after a call is answered by an extension user’s voice mailbox, that user can monitor/screen the caller as they leave a message.
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).