I did and still do email therapy and have found it very useful, especially becuase I find it difficult to talk about things in person so writing it down helps me a lot. I find that after a face to face session I forget everything as soon as I walk out the door but with email therapy I can refer back to it whenever I like.
My t happens to be very good at it too, sometimes I can read her response quickly and think it is very uncaring but then I will read it again later and realise that I picked up totally the wrong way- this is something to be aware of...misconception.