If you are using TEMAS, this will be extremely useful to you. It's such a great book, but there are no sample answers to the open response questions! Here is a package of 8 sample email responses to prompt #3, with scores and commentary ranging from 2 to 5 (the last sample in the packet is a score of 2).
I have attended the AP Reading as a rater for 4 years, one of which I scored email responses. I conferred with a colleague on these samples to make sure we were on the same page. The scores reflect my opinion based on my collaborative efforts and experience.
Students benefit from and appreciate seeing samples and hashing out elements of the rubric.