Your out-of-office message should be short and sweet. Don't try to be funny, because that can be misconstrued and give the wrong impression. If you can't keep it short and to the point, avoid including contact information, or else you risk giving your clients the wrong impression. They'll be left wondering whether you'll be back soon. This can cause a bad first impression and even a bad reputation.

See also - https://onlinegeeks.net/how-to-write-out-of-office-message-best-examples/