On a scale of 1-terrible, how bad of an idea is it to send an email to my ex?

It's been a month since he told me that he needed "a break" but that he didn't want to lose me and that he knows there's a risk that I might not be there when he figures out his feelings. The next day I told him to come get his things. We haven't talked since (except for the very bland email that he sent me on my birthday that I didn't respond to). I think it's pretty clear that there's no coming back - but part of me wants to make that official.

My draft right now is pretty blunt, basically "this was the right thing and I should have left a long time ago, I hope you can find some peace with it." I'd probably need to soften it up a bit if I do decide to send it. But it was good to get it out.