Emails are good for clarifying or adding to after the fact. You're trying to communicate STRENGTH and RESOLVE here . . . you can't do that via email, in my opinion (and I'm a big email GUY!).
We can't tell you what your "or else" is, Hope -- that's for you to decide. What are your core, non-negotiable boundaries of personal integrity? Now is the time (past the time, actually) to start figuring those out. If one of them is "I will not live in an open marriage," or "I will not live in a marriage where my husband is still communicating secretly with his affair partner" . . . well then you have some decisions to make. You don't need to know what those decisions ARE yet, nor do you need to communicate anything to your husband other than "Looks like we both have some big decisions to make."
Let HIM wonder what those are, and start to realize that he's not the only one calling the shots in the marriage anymore. And he SHOULDN'T be, because in his current state he doesn't have the marriage's (or your family's) best interests at heart right now. So that needs to be YOU.
