That doesn’t sound odd to me at all, depending on the company. I used to send a staff-wide note because they needed to know I would be out and they could plan accordingly if they needed anything. At my current company I wouldn’t do this, but that’s because it’s massive and I only directly work with a small team.
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.”

Between now and then, I recommend escaping the summer heat with a delicious Aviation & Tonic. Here’s my recipe:
I work at an animal shelter and I have included a picture of an adoptable pet when I’m on vacation – I don’t know if that comes across as annoying or not, what do you think? Basically, it’s “I’m out until X and I’ll return your message when I get back. In the meantime, take a look at Fluffiekins here (picture, link to bio). Will she be adopted before I return?”