Like the previous examples, the message doesn’t have to be lengthy – you just need to let people know the details, and who they should be contacting in your absence.
I include my boss because I have different backups for five or six different parts of my job, and my boss is more likely to know the nuances of which one is the appropriate contact than the person sending the email, so it’s more likely to get to the right person if she redirects than if the emailer tries to guess which one of the six contacts I listed is the one who can solve their problem. (My specialty is the “other things as requested” section of my job description; I’m sort of a jack of all trades around here. :) )

I had a colleague who simply never answered her phone or set up her voicemail. She still listed the number on her business card and email .sig, she just never answered or checked voicemail. When she took a new job another colleague inherited her phone number and when he went to set up his voicemail there were basically eight years’ worth of messages left for her that he had to delete.
Though you were ending with a “for everything else, there’s Mastercard” for a moment!