Depends on the system. Our Outlook is set up so that if you’ve got someone with an OOO in the “To” field, a note shows up saying that they are sending automated messages, and you can see the message. Convenient, since then I can add the person covering their stuff to the email without sending a second email.
A good voicemail greeting is short and professional, lets people know that you’ll get back to them, and invites callers to continue engaging with a call-to-action. You should also show your personality if you’re in an industry or role that allows that. If your industry is more conservative, however, you’ll want to keep humor and personal touches to a minimum. A greeting Your name Your company A simple explanation for missing the call (e.g. you’re away from the phone or are on holiday) A rough estimate of when you’ll get back to the person An alternative person to reach out to (if you’re out of office) An alternative mode of communication (if you prefer email or text) A call-to-action such as “Leave a message” or “Send me an email at [email protected]”

too short, though – most of the time you should give a date of return to set expectation (and so I don’t bug you again before you’re back)
I actually think that’s a really helpful out of office message? I appreciate how clear it is about who to contact in which circumstance (so you’re not having to do the awkward dance of trying to track down the right people while not inconveniencing the wrong ones), while maintaining a friendly-but-firm boundary around the vacationing person’s time (since none of the options include things like “here’s my cell phone number!”).