when I'm traveling, I don't necessarily have access to email, but I tend to let my students know that in advance. I also let them know I do NOT check email 24/7, yet some still expect me to.
Not saying you do... just making a general statement. Have had students email me at 11pm, then by 9am the next morning, I have at least 2 "why haven't you answered" emails. I work 9a-6p.