I’m Out of the Office. Really.

In January, Claire Davis started buying bathing suits. In February, she prepped videos to send to clients in her absence. In April, the vacation finally arrived, and the day before her flight to Hawaii, she sat down to write her first out-of-office message since starting her own business six years ago.

“Girl, you’re looking so professional,” Ms. Davis, a Spokane, Wash.-based career consultant for medical-sales professionals, thought to herself as she crafted the note. As she pressed the button, “I felt free.”

The feeling lasted about an hour. While waiting in line for brunch with friends, frantic texts started pouring in. Somehow, she had inadvertently set her auto reply to spam message everyone who’d sent her an email since 2016.

Some—like the close contacts texting her—had been inundated with hundreds of out-of-office replies, one for every email they’d ever sent her.

“It was horrifying,” she says, estimating the messages reached tens of thousands of people.

You’re going on vacation. All that’s left to do is unlock the magic wording that will free you from your inbox—and by extension, your work life. So why is it so hard?

Fiddling with the settings is just the start. Do you make a joke, open up about your personal life? How do you get people to leave you alone without making them feel abandoned or annoyed? Are they judging the length of your absence? Maybe it’s not even worth trying to log off at all.

“You want this time off, but at the same time you feel so pressured and so guilty,” says Ariane Ollier-Malaterre, a professor at the University of Quebec in Montreal who studies how workers manage the boundary between work and life.

The agonizing isn’t our fault, she says. Modern workplaces expect people to be perpetually reachable, and the pandemic seems to have shortened expectations for message-response times. Working from home, out of sight, we should at least be a click away, the thinking goes. A survey from cloud-software company Qualtrics earlier this year found that 49% of respondents did at least an hour of work a day while on vacation.

The out-of-office email has the potential to be your shield, Dr. Ollier-Malaterre says. Don’t apologize for taking time off. Remove email notifications from your phone, or delete the whole app if you’re brave enough.

That said, if you do ruminate on work matters while on vacation, taking a peek at your inbox might be worth it, she adds.

“Sometimes you’ll feel better because you can see that nothing is burning,” says Dr. Ollier-Malaterre.

Brian Brown long went with the standard out-of-office-template, trying to imbue it with a quiet sense of “No, really, I’m actually not here.” It usually didn’t work.

When co-workers received his out-of-office email, “The next thing you get is a second message that’s, like, ‘Hey, but I really need this,’” says the 33-year-old, who works for a tax-software company in Lehi, Utah.

He bulked up his notes, enclosing details about his whereabouts (his hometown in Southern California, a Tim McGraw concert, camping with no cell service). He wove in facts about the destinations. He noted why the canyons he was traipsing through on a recent day off reminded him of tax compliance.

Rather than messages demanding work, colleagues and clients now chat with him about his travels. He feels more connected to them, and seen as a person, “not a 24/7 robot,” he says.

The away message can be a thrilling canvas for office workers with poetic souls. Aaron Konter, a one-time aspiring screenwriter, joined the advertising industry hoping to do the creative writing he had long dreamed of. Instead, clients wanted the work done their way. Supervisors slashed his copy.

Then the Atlanta-area resident discovered the freedom of the out-of-office email.

“I didn’t have to get it approved by anyone,” he says. “I could just be myself.”

Subject line of one recent note: “Aaron is OOO (Baby Baby),” referring to Smokey Robinson’s and the Miracles’ 1960s hit. In others, he riffed on how addicted we all are to technology and implored the recipient to create a vision board to try to manifest what they’re seeking from him. He signs off with “Love, Aaron.”

“This is me,” he says of his away messages. “And if you don’t like it, that’s OK.”

Some out-of-office messages hit a nerve. I heard from an entrepreneur who was outraged by an automated reply from a vendor saying he was surfing the coast of France. Meanwhile, the entrepreneur and his team were rushing to wrap a behind-schedule project that required the vendor’s help.

To avoid having your message land poorly, use language that assumes you don’t know the recipient well and that they have more power than you, says Erica Dhawan, a St. Petersburg, Fla.-based leadership consultant and author of a book about digital communication.

Keep your note to two or three sentences, because being brief signals you respect people’s time, she says. Include an emergency contact and when you’ll be back. But feel free to hedge, publicly sharing a date that gives you some buffer time upon returning.

If you still have trouble turning on your vacation responder, help awaits. Iceland’s tourism-marketing office recently launched an online campaign starring three horses who clomp across a giant keyboard in western Iceland, majestic waterfalls flowing in the background. The gibberish their hooves type is available for anyone to use as an out-of-office reply.

Sigríður Dögg Guðmundsdóttir, the head of the marketing unit, assures me that the out-of-office templates available on the Visit Iceland website were truly generated by the horses, though humans proofread them to ensure no swear words in any language accidentally made it into messages.

The horse babble sends a message, she says, and that message is: “I’m on my vacation.”

Going all out, with an equine twist or not, just might do the trick. After all, Ms. Davis—the career consultant who spammed thousands of her contacts with the away-message misfire—came home from two weeks in Hawaii to just a couple dozen emails.

“They let me have that vacation,” she says. “Without really bothering me at all.”