A professional voicemail is vital in business, as it represents the brand and will be the first place that potential clients hear about the product or service. It's important that the voiceover conveys the style and tone, that best reflects the brand. For example, it could be chatty and conversational, cheeky, professional and business like or upbeat and dynamic. I will always work with clients so they can be sure that they receive a style that best reflects their brand.
I have a neutral London/British sound, that is genuine, natural and not forced. I would say that it doesn't need a great deal of producing, or processing. Less is more!