I’m talking about the opposite where you are the boss. I don’t send emails at night so my staff don’t feel the expectation to be constantly checking and replying to me. Just because I work weird hours doesn’t mean I expect my staff to.

If one of my team sends too many emails at weird hours I’d make a point of talking to them about their workload and life balance at an upcoming 1:1 to make sure things aren’t getting too off track.