I really hate when this happens and I will tell you that it's aggravating. There are a couple of reasons that it might happen based on my experience. He might feel things going to another level whether emotionally, psychologically etc. and he is scared a little bit and is pulling back. This could be due to commitment issues or having been hurt in the past. The other piece is that besides you, there might be someone else he is speaking to or seeing. If he is playing the field, then he might have found compatibility with someone else. Finally, he might have lost interest.
While I understand your frustration with him and his demeanor, personally I don't think the email was the best idea. Guys can be turned off by something like this depending on what and how the email was worded. Also, it might make him even "cooler" towards you.