There are three vital details that you want to make sure to include in any out of office message. First, be sure to include how long you'll be out. You don't want someone following up on an email when you're still out. Second, it's a good idea to be clear about how reachable you'll be . Will you be checking your work email once a day, a couple times a week, or not at all? Don't feel pressured to say that you'll be checking your emails if you really need the time away. Take that time! You've earned it. Third, make sure to give them a way to get in touch if their email can't wait, whether that is your cell number or a co-worker whose agreed to cover for you.