A relatively unprofessional one — like mine, for instance — does the opposite: It encourages prospects, recruiters, and potential connections to run in the other direction.
Voicemails need to maintain a professional consistency that’s aligned with the entity it’s representing. That said, the structure can vary depending on the situation. There’s no template set in stone. In fact, trite and generic should be off the table. The goal should be a balance of uniqueness and practicality.

Optimum is the first landline telephone service provider in the U.S. to launch High Definition calling. HD calling is the next generation of voice technology that gives you less background noise, sharper sound quality and increased clarity in your phone conversations. To experience HD calling, customers and call recipients must subscribe to Optimum Voice and use HD-capable handsets.
In an ideal world, voicemail would be unnecessary. There would always be someone available to take customer calls and no one would complain about their calls not being returned and/or rejected. But of course, this perfect world isn’t possible. That’s why it’s important to give your callers options when you are unavailable. For example, aside from leaving a message, callers can also choose to listen to some relevant information about your business (such as a list of your services, your address, directions, hours of operation, and more).