Writing an effective out-of-office message is a key part of running any business. Although it may seem so simple, an incomplete or unclear out-of-office message will cause problems before you leave as well as when you return.
6.) Bienvenido/a a John Doe. Nuestras líneas de teléfono no están operativas durante los períodos de vacaciones. El horario de oficina se puede encontrar en nuestra página web www.johndoe.de. Le damos las gracias por su confianza y le deseamos a usted y a su familia unas felices fiestas y un próspero año nuevo.

I think this is great. A little too long, but it would work well as an internal reply in a large office with the right kinda culture. I’m imagining how useful it would be in my previous office with 300+ people that always had some “fire” or another to put out. I also appreciate how it protects the sender’s time off–at no point does it say “ok, fine. contact me.”
I find it rude, as well. If someone is emailing you (the royal you), it’s because they need something. Saying you’re just going to delete it without also giving that person a Plan B contact is totally rude. It sucks having to go through emails, it does. But it’s part of the job. In my role, I get requests from internal colleagues and from external partners. Even though I provide those partners with an alternate email to send their requests, it’s still my responsibility to make sure that the requests that were sent to me in my absence were handled. Saying “everything I’m sent will be deleted” just Would Not Fly in my industry.