People have short attention spans these days, and you should always craft your communications for the lowest common denominator with something as universal as your voicemail.
To improve a a business voicemail greeting, keep these eight rules at the forefront of the creative process: Avoid turning customers off with overused and impersonal phrases like “your call is very important to us..." Avoid leaving customers unsure by not immediately telling them the business, department, and/or person they’ve reached. Avoid leaving customers confused with too many details and complications; just keep it simple. Avoid messages longer than 25 seconds. Do apologize for being unavailable at the moment. Do invite the caller to leave a message. Do tell the caller when they can expect a return call and actually follow through within that timeframe. Do tell the caller about any applicable alternative options of contact and information- website, live chat, email, social media, or emergency numbers. Voicemail Greetings 101

The above eight rules of engagement for voicemail greetings may sound easy enough, but they’ll require some practice to get just right. Let’s look at some examples to provide some context in how to apply the rules to various types of greetings and situations.
To get voicemail messages to their intended recipients faster, many speech-to-text providers now offer voicemail transcription services. Nuance is one such company, and Dan Faulkner, its senior vice president of mobile, says the service is widely popular. "We find that the voicemail-to-text service is incredibly sticky," he said in a recent interview with Speech Technology magazine. "When people get it, they don't listen to voicemails anymore."