If you don’t know it by now, you might never know. Voicemail greetings are incredibly important to users. It conveys identity, character, and image to callers. In an increasingly digital world, where business is conducted online and over the phone, phone presence is increasingly important. As such, your greeting is a crucial part of the platform. While there are a number of obstacles to be aware of, utilized properly, voicemail greetings can be incredibly helpful and beneficial; therefore, its in users best interest to invest themselves in creating a quality recording.
a standard greeting as per Option 5 minus the mailbox user's name, followed by the fixed system prompt, "Begin speaking after the tone, then hang-up when you are finished or press any key for further options."

28. Hello, you’ve reached [your name]. I can’t come to the phone right now, probably because I’ve just stepped away from my desk, but possibly because I’m trapped under something heavy. Leave a message and I’ll call you back within one business day — and if I don’t, please send help.
Chances are that when someone takes the time to leave your business a voicemail, it is because it’s important that their message be communicated and left in the right hands. There’s nothing worse than calling a business only to hear that the voice mailbox is full or that the greeting is too quiet, too fast, or too confusing.