Its certainly okay to contact between sessions if your T says its all right. I think especially with the email thing-- I mean, they have a choice of when, where, and how many times they check it. They can do that in the middle of the night or whenever they have time, 5 times a day or 1 time a week, or whatever inbetween. Its all up to them on their own timetable. So if they say its okay, its okay. Trust your T (do you?) to let you know if it is not all right to anymore.

(p.s. I know its hard! )