I have a confession to make: I haven’t recorded a new voicemail greeting since 2014. In the past four years, I (hopefully) have become more articulate, poised, and self-assured. But hear my voicemail recording, and you’d think I was still new to the work world, a little unsure of myself — and probably not an authority. Obviously I need toupdate it. And if you haven’t changed your voicemail greeting in over a year, you’re likely in the same boat. After all, a professional voicemail recording boosts your credibility, makes you seem more competent, and encourages whoever’s listening to it to continue the relationship. A relatively unprofessional one — like mine, for instance — does the opposite: It encourages prospects, recruiters, and potential connections to run in the other direction. With that in mind, I’ve written 18 unique voicemail greetings for every situation. Pick your favorite, practice a few times, then record your new voicemail.
There is no way to know who has listened to your voicemail unless the caller leaves you a message.

I am not a voice talent, and I hate the sound of my own voice. Every time I lose my cell phone (daily), I call it from another line to help myself find it. And every time I do this, I wish my voicemail message sounded…different. I’m always reminded that I should sit down and rerecord it, so it makes a more professional first impression.
You should acknowledge that right off the bat by apologizing that they couldn't reach you directly.