Email is one of the top tools for business communication. People expect swift responses to their requests. If this expectation will not be met because you are away from your desk, your client or colleague needs to know.
She continues: “However, there should be a way for whoever is emailing you to have an urgent request handled, and that should be included as part of your OOO as well as being known to your work team (supervisor and colleagues). That might look like including a coworker's email on your OOO or it might simply involve setting a forwarding rule for while you're away, so that your email goes to the colleague who's covering.”

This might seem obvious, but make sure you clearly state and restate the dates you’ll be out of the office. Even if you put the dates in your subject line, you should also repeat them in the message body. It’s hard to over-communicate here. State exactly when you’ll be back, and whether or not you’ll be responding to calls and emails while you’re out. If you’re on the road but are responding to messages, let everyone know if you’ll be unavailable for an extended period (while on a flight, for example), if you’ll be in a different time zone, and in general, that they should expect a delay in response time. All in all, set realistic expectations and strive to be as specific as possible.
But this absence of basic travel cybersecurity is a problem. Email is the number one threat vector for socially engineered attacks. An automatic reply message not only sends the information to designated contacts, but it also bounces back to people who send phishing emails. Threat actors use any details found in OOO messages to craft targeted social engineering messages. Well-targeted messages build trust that threat actors take advantage of.