My Boyfriend Saved Love Letters From His Ex.

I recently found out that my boyfriend of nine months still talks to his ex-girlfriend. They had a pretty bad breakup and ended their relationship over a year ago, but last time I asked him about her, he said it had been months since they'd spoken. Recently I found out that he still has a bunch of love letters saved from when they were together and that he texts her every few days. He has told me that getting back together with her is 100 percent out of the question. I know he loves me, and she lives on the other side of the country so it's not like they meet up, but it still bothers me that he talks to her so much, and as far as I know, she doesn't know he is dating someone else. Am I wrong for being a little upset about this? Is there a good way to bring this up or should I just let it go?

Breaking up with someone isn't as simple as: Delete file. Empty trash.