Whether you’re out for the day or are off for the week, the first rule of an out of office voicemail greeting is: let callers know when you’ll be back! You’ll save them the frustration of continuing to call and yourself the hassle of listening to redundant voicemails. It’s also a good idea to set the expectation of whether you are answering messages while you’re away, and who they can reach for assistance in your absence.
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.

#9 “Hey, this is Bryan, sorry I missed your call. You can leave me a message, or shoot me an email at bryanallain at gmail dotcom and I’ll get back to you. Thanks.”
Expanding on the simple approach above, let the caller know who they've reached. This will not only eliminate people leaving voicemails by mistake, but it will reassure the caller that they have called the number they intended.