For me if someone schedules a meeting before 08:00 and after 15:00 it is an automatic NO.
Early morning mail checks (before 07:00) is done only when I am on call and to see if there was any emergencies in the prior evening production run that I missed. When I do that my day starts at that time! I adjust the end of day time to allow for the early start. Normal hours for me is 07:00 to 15:30.