I am on sick leave with no access to emails and phone calls. Hence, kindly expect a delayed response.
My colleagues have this weird habit of not using out of office messages, but instead, sending all staff or all manager emails before they go on vacation letting everyone know they’re going to be gone for x amount of time. It’s really odd. I do not do this.

I used to work with someone who had a message telling people she only checked her email twice a day. You pretty much needed to call her if you needed anything outside of those times. (She worked in a remote office.) I think she had read one of those books on efficiency that recommended scheduled email time. But there were problems with this: 4. My department often had to email attachments or text to illustrate our questions/concerns. And we were on deadlines. Reading a page of text over the phone was not an efficient use of anyone’s time 5. She did outreach & was often out of the office on site visits, trainings, or travel to these places, but never ever set her OOO for these, because she was “working.” However, she was effectively not available to read emails from other staff until after hours on those days.
If you are checking emails while you’re out and are responding slower than normal, state that, suggests Jill Gugino Panté, director of the Lerner Career Services Center at the University of Delaware. “If you don’t have access to email and can’t return messages, state that as well,” she says. “The clearer you are in your messaging, the better.”