Should my ex force me to deal with l with his "common law wife" re: our parenting schedule for our son?

My ex left me for my best friend (not!) when our son was 3. This was I moved here from another state, left my great job and career, to be with him and after using in vitro to have our child. I have let the past go, even though he treats me like I cheated and left, to him.
He will not co-parent with me. He just ignores our son until it's his weekend to have him. He does not go to his orchestra concerts, or any other school functions. When we need to do the parenting schedule (he only communicates with me via email - always signed both he and his "wife"
They continue to try to force me to communicate with her by having her send the emails (i know because she refers to him in the 3rd person) I didn't sign on to co-parent with her. I think it's really cruel of them and causes pain for me every time i have to read their emails.
Isn't this ridiculous? It keeps all of us from healing by adding salt to a wound - It is just another one of his control freak mechanisms. I just want to forget what they did and deal with him strictly as my son's dad. Her sending me emails is a very unhappy reminder of how much my life they both took from my son and I.