Both your customers and your employees need to know how long your business will be shut down for the holidays. Provide notice well in advance. Depending on the types of services you offer, you may need to start notifying customers as early as a month out. It would be best if you were to provide these important notifications at least two weeks before the holiday shutdown. Employees should also be reminded regularly that the company will not be open during those important days.
But I also believe there’s meaningful power in the mundane cultural norms we set and practice. Email, for better or worse, makes up a large chunk of how knowledge workers communicate. So much of this communication is muddled by broken email habits and larger anxieties around performing productivity. We’re constantly nervous about asking too much of others or doing too little on behalf of our coworkers. But we’re also stuck in work patterns that force us to communicate constantly and normalize working and demanding things from colleagues at all hours.

My favorite OOO to set is something like this: “I’m at sea from X to Y with very limited bandwidth. I’ll reply to urgent emails as soon as possible (but there may be a delay); if you don’t hear back from me by Z, please resend you message.”
I will find a few moments of holiday bliss once they watch Elf for the seventh time this month. I’ll seize the quiet to check my email once a day. I will only respond to urgent matters but will reply to all emails upon my return.