Website: https://www.amazingvoice.com/blog/10-best-professional-voicemail-greetings
Friends and colleagues speak to each using first names only. So do people of authority. They do not call each other and leave voicemail messages asking for Mister, Miss, or Mrs. Therefore, when you call a person you want to do business with and you leave a voicemail message, refer to them by their first name only. Don't say mister, miss, or misses. Don't say their last name. Begin your voicemail message by saying only "hi/hello" followed by the person's first name. Or, you can even forget the "hi/hello" and just say the person's first name. That is how you show confidence and authority and separate yourself from weak salespeople.

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.
The most engaging messages are slightly unique in nature. They combine a mix of clever scripting and music. Slight humour is often used to promote a product or service and is usually quite effective. It's also very important to choose both the written and spoken tone that appeals to the characteristics of your audience. If your target market is the younger generation, a script that includes slang words and is quite laid back would be an excellent choice. If your target market is primarily business professionals, then a more articulate choice of words would be more suitable.