There’s a grim, apologetic vibe to these messages — I’m sorry I’m taking time for myself but I’ll try to check in on occasion! They’re a vivid reflection of a work culture that valorizes constant productivity and the near-total overlap of work and life. But they’re also do a terrible job of what they’re intended to do, e.g., set realistic expectations for both sender and recipient. A vague OOO message traps both parties in an uncomfortable liminal space where both productivity and rest go to die. The original sender is left unsure if they’ll be getting a timely response or a whether the email will go ignored for a time or forever. The original recipient has taken what is a rock solid excuse (time off) and cheapened it, offering a backdoor for email guilt to creep in.
On the other hand, there may be times where you’re so embedded in a project that you truly need to stay connected while you’re out. If that’s the case, say so clearly with a message like this: “I’m away but will be checking messages regularly, so don’t hesitate to contact me directly at any time.” Saying anything less than this may cause people to try to respect your time away and work around you, which in this case could create problems.

If it’s not important and you’re just a little bit bored then you can amuse yourself with these fun facts until I return. When hippos are upset, their sweat turns red. Bananas are curved because they grow towards the sun. There are approximately 100,000 hairs on a human head. You can buy eel flavoured ice cream in Japan. A group of jellyfish is called a smack.
I do that for most cases. Occasionally I’ll change it to “I’m out of the country and will not have phone or email access.”