He will get the message only through your actions.
Respond only to items regarding the children, and only on the terms you outlined.
You could set a further boundary for 1 email a day, you will look at the first, and delete the second and third..........
He will learn only from your actions that follow what you state to him.
Doing it by email will help you keep a legal record of what you say. They have a way of rewriting history, faulty memory about what was really said.
Limits will give you space and time you need to heal.
Bomb 1/06 D dismissed 11/07, attempt reconciliation. Premature. Divorce final October 31, 2008. OW looks like bad history. Over. Still hopeful. Baby steps. In R with my X.