As mentioned above, alerting callers that they won’t be getting an immediate call back is of upmost importance for an entity’s reputation and a caller’s satisfaction.
Rehearse or write down your message before recording it. Remember that old saying “practice makes perfect?” It’s certainly true when it comes to creating an electronic greeting. The more you’ve rehearsed, the easier the message will be to restate. If you don’t have time to practice, writing down the greeting before recording it – and then reading it aloud from the paper – may help you stay focused on the correct wording.

Hello, you have reached the dental office of Dr. X. We are busy assisting a patient now, but will call you back as soon as possible. Please leave your name, reason for calling, and your number. If this is an urgent enquiry, please call 911. In this case, the dentist is giving a reason for not being available and they’re providing a way to prioritize the patients who need the most help. They’re also leaving an emergency number for the most severe of situations.
The general voicemail greeting is used as the default voicemail greeting if you don't set any other greeting type. Occasionally, during events like power outages, even if you've set another greeting, your personalized programming might be wiped out. Or you might simply forget to change the greeting after returning from vacation.