It is no surprise that your actual voice mail greeting must be delivered in the same way: Professional, clear, brief, and to the point. In a previous blog, "Marketing Messages on Your Cell Say You Mean Business," some techniques for making a professional voice mail greeting were discussed. There are many similarities between leaving a voice mail, and producing a voice mail greeting. You want your callers and receivers to hear a confident and professional person on the other end delivering a coherent message. You should introduce yourself to a prospective client in a personal way. An email doesn't generate much discussion, nor does it necessarily show you went the extra mile in contacting the client. Generating conversation. A professional, well conveyed voice message shows the voice mail receiver that you are confident and well-spoken, and that there is a person behind the message. Emails can be prepared, edited, and revised unlike voice mail messages An email or email chain thread is documentation of a conversation that can easily be referenced In an email you can include a phone number, address, website, etc that may be hard to remember or record through voice mail communication Emails can be forwarded, CC'ed, and blasted.
We’ve all had to make phone calls we wish we didn’t have to make. While the phone rings, we pray the person doesn’t answer, so we can simply leave a voicemail message.

Why not shorter than 20 seconds? The voicemail indicator will tell the contact how long the message is, and if it’s just 5 or 10 seconds, it may seem like a spam call or a wrong number, which means they won’t listen to it at all. Messages between 20 and 30 seconds seem important enough to listen to but not so long that they’re off-putting for the contact.
If you want your prospects to get back to you, you better sound exciting. If you have a monotone voice or sound generally unenthusiastic on a voicemail, you are almost certainly not going to get a response.