An out of office message is a compact text that conveys the most important facts: How long you’ll be unreachable, when your contacts can expect an answer, (optionally) the reason for the absence, and, if necessary, a personal note. A referral to another email address, e.g. to one of your colleagues, is often helpful or even necessary.
What we need in our work communication is not more professional politeness or less formal, chat-based messaging applications like Slack. We need honesty. The problem is that we’ve conditioned ourselves to see honesty as self-indulgent or disrespectful. I’d argue the opposite is true. Honesty, even if it’s a bit more inconvenient for all parties in the moment, pays dividends later. It builds trust. When my partner Anne Helen Petersen and I were interviewing people for our forthcoming book on remote work, a frequent lament from both middle managers and workers was that they didn’t feel like they knew how to succeed in their jobs; that they were guessing what their superiors and coworkers wanted and, even when they asked, they didn’t quite trust the responses they got back.

Have you sent a proper farewell email to the whole office, thanking everyone and wishing them well?
If you’ll be away for a portion of time observing a holiday, create a cheerful auto-reply in your absence! Instead of my phone, it’s the jingle bells that will be ringing until 1/2; I will be out of office until then, please expect a reply with 24 hours of my return. I’m leaving on a jet plane! The Stern Firm will be out of the office until 3/4 on a company-wide retreat. We will respond to all messages promptly upon return.