With a slightly modified email address to mirror yours, they can easily impersonate you using the personal information provided in the OOO message and exploit your absence. Knowing where you are and how long you may be gone can lead to an attempt to initiate a transfer of funds or access confidential data. They might even go the extra step and reference how great their “trip” is going just to make the message appear genuine.
Setting an auto-response email is probably not the first thing on our mind before we jet off on holiday. But if we don’t do it, we risk eroding the trust between ourselves and our customers. It’s important to remember that response time is a non-verbal sign that shows clients and business partners how responsible and professional a company is.

An out of office message is a compact text that conveys the most important facts: How long you’ll be unreachable, when your contacts can expect an answer, (optionally) the reason for the absence, and, if necessary, a personal note. A referral to another email address, e.g. to one of your colleagues, is often helpful or even necessary.
Hello, and thanks for your email! If you’re getting this message, it means I’m taking my annual two-week creative sabbatical—working on personal projects that inspire me, so that I can return to work full of fresh ideas for my clients, like you! I’ll respond to your note once I return to the office on [DATE]. In the meantime, here’s a question: What inspires you? Do that, today.