Anybody that might need me that quickly should have access to my calendar and can see I’m in a meeting. Anybody that can’t see my calendar shouldn’t expect a reply in an hour unless I’d said I’d be available or something.
I say “I am out of the office without access to email” to avoid the expectation that I’ll check on vacation. With a contact for anything urgent given.

After I tweeted this example, dozens of people sent me examples of OOO messages they’d set or particularly good examples they’d seen in the wild. One example from a boss (via a TikTok) who offers emailers a decision tree of sorts. “Option 1.) Wait it out. Ask yourself, ‘is this urgent and important?’ If not, take a beat…you and I will be better off with this expectation set now,” the email begins. This one stands out because it’s extremely detailed, manages expectations and also offers who to contact in different situations. It models good behavior of taking time off, but also gives the original sender a variety of option. Most importantly, the responder forces the original sender to assess whether this is actually an urgent request.
There’s nothing awful or offensive about this message, but it’s also not very good. Yes, it provides the courtesy of letting the sender nominally know that you’re going to be slower than usual to respond. That’s nice. The problem is in this bit: “may be slow to respond to email.” Another popular variation: “might be slower than usual to respond.”