So my friend "broke up" with me in an e-mail which said...?

i wouldnt worry about if this is normal. your friend has obviously expressed his feelings concisely to you. you just be sure to take note of what this friend has done, if and when he comes back. the "why" is not important, just look at the facts. dont trouble yourself looking for answers from someone who wont even talk to you. move on, and if this friend comes back, give it to him real good to make sure he understands how he made you feel.