Should I send him a message telling him how much he hurt me?

I (37F) was seeing someone (37M) I really liked. We had open, honest conversations about not seeing other people, building trust, and taking things slow. Out of the blue 3 months down, he messaged me one night saying he had coffee with someone he met earlier that day and that it ended in a kiss and they're looking forward to seeing each other again. He said he didn’t think it was a date and felt he was being “honest” by telling me after the fact.

We had previously agreed that if anything changed or if we were interested in seeing others, we’d talk about it before acting on it. He broke that agreement, and it really shook me. I ended things right away, but I’ve been left grieving deeply.

I wrote a message (that I haven’t sent) explaining how much his actions hurt me—not because he kissed someone else, but because he didn’t speak to me first. I want to express how it broke my trust and impacted me emotionally. But I’m torn:

Would sending it help me get closure? Or does it give him more emotional access than he deserves?

How would you feel receiving a message like that, especially after you've already walked away?

Would love your honest perspective. Not trying to win him back. Just trying to understand if expressing pain directly helps or hinders healing.