Is it wrong if your ex still speaks to a friend he slept with whilst you were broken up?

You really can't know what they are talking about. I dated someone for a while who was in the process of a divorce, then she decided to get back with her husband. She would send me what you call "general chit chat" type of emails and since I still considered her a friend it was fine. Then, the emails started in on all these relationship problems she was having and I stopped dealing with her out of respect for the guy, even though I've never met him. Yeah, if I was you, I probably wouldn't like it very much and I didn't think he would like it which is why I stopped.