Exactly. It doesn’t matter if I’m sitting on the beach, on my couch, or in a hospital bed–I’m not reachable and you’re gonna have to wait until I get back or contact someone else.
Hi, I will be away from my desk [MM/DD] until [MM/DD]. For urgent matters, you can contact [name] at [email] or [phone]

An out of office message is a compact text that conveys the most important facts: How long you’ll be unreachable, when your contacts can expect an answer, (optionally) the reason for the absence, and, if necessary, a personal note. A referral to another email address, e.g. to one of your colleagues, is often helpful or even necessary.
There ought to be a word - and perhaps there is, in German - for the mix of feelings that accompanies composing and activating a holiday out-of-office message. There's smugness, of course, and a gratifying sense of laying down one's virtual tools after a horribly long shift. But for many of us, these nice feelings are tempered by the knowledge that in two weeks, refreshed but depressed, we will have to trawl through hundreds of emails, many of which will be conference room notifications for meetings about crises that have passed.