Closing a window in mail

A message I sent got shot back to me and I cannot for the life of me figure out how to close the window. It is driving me crazy. I quit mail but when I open it back up the message failure reappears. I cannot scroll to the bottom of the message where I believe I can actually close the window and I can only minimize or maximize the message in the top left corner, not close it. Any suggestions?

Welcome to the forums! Please read the link in my sig and post again. It's helpful if we know more about your system and what you are seeing and have done.

If it's actually a window your want to get rid of or close, you should be able to close it if it's the frontmost selected window by just hitting your command + w keyboard keys.