I have the same situation.
He said he doesn't mind if I wrote him emails but it would be better if I could tell it not write or I can read it in sessions (I did it once but I don't like it).
I think it could be the same with your T, if you say it in email, you don't talk about it and it's not that helpful.
In my last email I said- please help me to talk about it with you at session.
You can send email and then talk about those things you wrote.