Even in today's fast-paced world, customers don't like being greeted with an automated message. According to the New York Times, callers of a certain age are put off entirely if they are answered by a voicemail instead of a real person.
You should script out your greetings, rehearse, and find a tone of voice that is reflective of your professionalism and your company’s personality. If applicable, your tone and your message should take into account that certain industries and companies are more conservative than others.

Mood can also play an important factor in your recording. Record the greeting in a quiet place, remember to smile, and focus on leaving a positive message that’s sure to please your customers. (Tendant provides an example script you can leverage for your voicemail greeting.) Cut through the noise by speaking clearly. From honking horns to spotty cell service, callers often have their own background noise to contend with. The last thing you want is a missed message due to a lack of clarity, so make sure your outgoing greeting is clear, concise, and recorded at a reasonable pace.
After hours, though, it could be easier to send callers directly to a central voicemail box. This can work well for a small business that won’t need to field a lot of late-night calls.