KR, what you say here is no problem at all. I don’t think anyone says what you want to communicate right there is a bad thing. In fact, it’s a good thing. But, that is not what your earlier text communicated.

I communicated pretty much what you quote above to OM, in person. Not that it did much good re ww trying to stay in contact, but it did chase OM away. I made sure he knew the consequences would be very, very bad for him and his family if he either initiated contact or responded to attempted contact. It worked from his end. For five years anyway.

You should expect, based on her NC letter reluctance, that contact will continue and but it will go way further underground. So anything you can do to put the fear of god in him should help NC in general and to some degree.

But do it for yourself. Don’t even bother to tell your wife what you do. Just do it. Like exposure.

You will know contact is happening when what you tell him gets back to you through her anyway.

I figured this. I will work on the letter, call him and that's it.
However, I will still in my mind know that she refused to sign the NC Letter. That's a hard one to get by.

I will have to continue policing her like a hawk.

Exactly

Let it go. She may be embarrassed to make a big deal out of what was a fairly minor flirt, as far as I can see.

I send the OM an email like mine, add in the part about not responding to anything she might send (Jennifer H had us do that in our NC).

Send it off and move on. As someone said, if your W ever mentions your email, then you know there is contact and you need to step up the situation.

Compared to most of us this is not something worth a life long crisis, KR. Work on your marriage, make it affair proof so she won't want or need to look outside.