Men Please Translate: What does it mean when you send your ex-boyfriend an e-mail about...?

Men Please Translate: What does it mean when you send your ex-boyfriend (that just broke up with you three months ago from 1yr1/2 relationship) an e-mail about how you were sorry for your mistakes in your relationship and how you are grateful for what you have learned (and I felt it was pretty pleasantly toned e-mail) from your relationship with him (along with info about things going on in my life like I am applying for a promotion and thinking of going back to school)--- then he responds with: "Thanks for the e-mail. I appreciated it" and that's it. It just seems so incredibly brief. What does this mean?