Late night emails would not concern me. Like SD and others said, some people are night owls. I like email precisely because I can email at weird times and not disrupt people.

T3 sees her first client at 1:30 pm, and her last session is at 8:30. She always runs late; I see her at 8:30 so we can run over (her suggestion) and I have left there as late as 10:30.