If anything big changes- address, phone, etc.- make sure you correct your voicemail early on. Keep It Short; We know, we know. We just gave you all this information and we’re now telling you to ‘keep it short‘. But, a professional voicemail greeting (or any for that matter) shouldn’t go beyond 20-25 seconds.
It is really important to strike a balance between coming off as too cold, conservative and impersonal with making your message too out there, long or eccentric. If you can create something memorable, it will help engage a caller, or potential client. Go too far off the deep end, and you’ll scare them away

Users often don’t invest enough time into their messages, resulting in incomplete, unprofessional, or otherwise under-whelming greetings. Sure, crafting a greeting doesn’t sound all that complicated; however, there are a number of pitfalls users can fall into—i.e. informality, terseness, sincerity, lack of direction, and more. While none of these sound too catastrophic, they are often interrelated. As such, they tend to worsen any problem. For example, humor can cause informality, worsen ambiguity, and weaken sincerity. That being said, users should strive to avoid ALL these pitfalls.
Sounding professional on the phone is extremely important for a variety of reasons. It is especially important if much of your business is conducted over the phone. In this case, it is essential that you know how to maintain professionalism, since it will give a good impression of your abilities and skills.