I am currently out of the office and will be back to work on (insert date). If something urgent comes up, you can let me know by emailing me with the word “URGENT” in your email title and I’ll get back to you as soon as I can.
I might sound nitpicky but the language is important. “Might” or “may be” or “slower than usual” are vague and don’t offer the sender all that much information about when you’re really going to respond to them. Worse, they do a horrible job of protecting the time of the email receiver who, as the responder notes, is not in the office! Such a responder implies that, not only will the vacationer reply to the email, but they may not even miss a beat. They may be slow to respond, but they also might not.

On the Inside My Organization tab, type the response that you want to send to teammates or colleagues while you are out of the office.
I worked at a public agency and would have different out-of-office messages for internal and external. I was chastised for having a “too informal” message- because the idiot talking to me didn’t realize me saying “I’ll be back next Tuesday for the big staff meeting” (or whatever) was just for co-workers and not the public. I told them but of course it didn’t matter. So from then on I always made sure to start my internal OOOs- “Hello Company X comrade…. blah.” So it was clear which was which. I am not able to respond to your email promptly because my husband died. I will not be accepting zoom invitations. Please do not respond by suggesting future alternative dates. I don’t know when I will be able to speak without crying.