Protocol for when you should use an out-of-office message will vary by job and industry, but generally, you should set an OOO message when you’ll be out for two or more days.
We have one key administrative assistant who works part time and I always forget — I appreciate that she sets an OOO every day because her department is very deadline driven and it helps me to remember that if I need something from them, I need to connect with her in the morning. We also have some staff who work the school year calendar and others who are year round; the OOO is so helpful in the summers!

The auto-delete policy - which is optional - follows a piece of government-funded research on work-life balance, which Daimler carried out in 2010 and 2011 with psychologists from the University of Heidelberg. The company now trains managers to set a good work-life example, and encourages them to set aside time when no meetings can be scheduled. This is supposed to be a time when workers can concentrate on their job, or take time off for any extra hours they have spent in the office.
First, and most importantly, let the people trying to get in touch with you know when you’ll be gone and when you’ll be returning. There’s one more date to add — when they can expect for you to return their message.