A professional voicemail greeting is a recorded message that welcomes callers to your business when no one is available to pick up the call. For a polished call experience, the greeting should reflect who the client is calling – whether a general business number, department, team, or individual – and when the customer can expect the call to be returned.
As a bonus, here is an example of our own holiday voicemail greeting here at OpenPhone:

Call Detail Records are provided in the Optimum Business Account Center for all incoming and outgoing calls made to and from your phone line. You can view and download Call Detail Records for the current bill period and up to three prior bill periods.
When you create a professional voicemail greeting, it can be a good idea to think about what your callers might want to know. After doing so, you can make a list of points to cover in your voice message; it might also be a good idea to write out the entire greeting on a piece of paper. The ideal message should be somewhere between 10 and 20 seconds, so you may want to time yourself repeating your message before you record it. After composing your telephone message, it can be a good idea to get a second opinion of this greeting so you can make sure it sounds professional. Writing down a voicemail greeting helps prevent mistakes when recording it.