You can configure automated reply messages to encourage customers to submit their queries.
Most awkward/painful one I ever saw was a former co-worker. ~10 years ago when he left on paternity leave, he said as much in his out of office. The baby was stillborn. It stayed up for the month or so until he returned. Those of us in the same office of course knew the situation, but we regularly communicated directly with multiple offices in different states and countries. The very first time I saw it I was overcome with dread about how many congratulations he would receive and have to tell the story to. I was much younger and afraid to rock the boat then, but I think now I would push his manager and IT to use their ability to access his account and change it.

Different people may create different out of office messages based on what information they want to convey. It can be a simple notification of your absence and the date of your return. Your message can also point the person to some other person or resources to help them when you are away. Let us look at some of the most common examples and templates you can take help from when creating your auto-response out-of-office message.
My OOO is almost always “I’m out of the office and will be returning on x date.” My email sig has instructions along the lines of “for questions on x, email this list” for a couple of the more common areas people would contact me about that might need an urgent reply (as the lists go to more than just me, obviously), but most people have finally figured out to contact those lists to start with, anyway. If I were in the middle of a project or something that needed to be moved along in my absence, the project teams usually know when we’re out, but I’d put a back up in that case, if needed, but generally there’s not much to be gained by a longer OOO from me.