I haven’t set up an OOO message since I got my first smartphone. My usual method is to glance at an incoming work email and forward it to the appropriate person, or maybe write a one-liner response saying I’m out and will answer next week.
A simple greeting like, 'Season's Greetings,' or 'Happy Holidays," is appropriate, followed by, 'I hope the season is treating you well. I wanted to thank you for your business this year and wish you and your team a Happy New Year. ' A sign-off of, 'Regards' or 'Best wishes,' is inclusive and business-friendly. What's a good out of office message?

Hi, I will be out of the office starting [MM/DD] through [MM/DD]. If you need immediate assistance during my absence, please contact [name] at [email] or [phone]. I will respond to your emails as soon as possible upon my return on [MM/DD].
On the other hand, there may be times where you’re so embedded in a project that you truly need to stay connected while you’re out. If that’s the case, say so clearly with a message like this: “I’m away but will be checking messages regularly, so don’t hesitate to contact me directly at any time.” Saying anything less than this may cause people to try to respect your time away and work around you, which in this case could create problems.