I have done it in the past and it did work surprisingly well. I would send long emails and get a lengthy reply back with suggestions on how to go forward and what to think about for the next time I emailed. It didn't quite work out for me as I was also seeing my normal therapist at the same time, which I shouldn't have been doing. But on it's own, it was good therapy. I guess it would depend on the therapist but the one I had was used to working this way so she was very good at giving detailed responses answering all my concerns. I would say definitely worth giving it a try. Good luck!