Be aware of your tone. Keep it clean and simple. Sullivan says: “Even if you work in a casual office environment, the people emailing you may not. It's fine to have a light tone in your communications, especially when you're in an email conversation with someone directly, but your OOO is more of a blast message—including a cat meme or silly quote could backfire if your OOO goes to, say, a new client prospect or the sales director at a company you've been trying to engage.”
First things first: let’s go over the basics of an OOO email. In your away message, you typically include the following: A quick “I’m out of the office” phrase. The date or time range you’ll be out. Who to reach out to in case the sender needs immediate attention. A sign-off.

Although out of office emails are usually used when a person’s on holiday, they can also be used in a number of other circumstances.
Over time, I began to suspect that those who might be telling the truth (of which I suspected there were very few), would mention their relationship to the person and possibly the cause, for example “My grandmother just passed away after surgery.” The ones who left it wide open (“someone close has recently died”) led me to imagine that it could be a random person in their city that they read about in the news, their goldfish, or perhaps a distant relative who had passed away in the previous few years.