Your phone system can be a powerful marketing tool for your business, and that includes your voicemail greeting. If you want to utilize this opportunity to throw in a quick humblebrag and keep callers informed of your awards and accolades, there are a few best practices, you should follow. First, keep the self-promotion brief and appropriately placed within your voicemail message. Don’t promote yourself and your products/services in the same greeting, and finally, only include current achievements in your business voicemail greeting.
Doing this helps you understand what the prospects are looking for and what they are expecting from you which will in turn help you to cater to them better.

“Voicemail is a highly available, affordable, easy-to-use tool that can be leveraged in many ways to help businesses manage their communication needs,” says Holly Hinze, director of Commercial Products for Spectrum Business. “Business owners may not always be available to answer live calls, which makes voicemail still a necessary function,” says Hinze.
17. "Hello! You've gotten the voicemail of [your name]. Leave your name, contact info, and the answer to the eternal question ‘Which came first, the chicken or the egg?' Anyone who gets it right will receive a call back."