Upon composing and sending email in Hotmail, my sent box shows other emails from my inbox were included in that sent email.

Question: I have no groups set up in Hotmail. I compose an email, and I send it, plain and simple. Upon checking my sent box, I see that not only my email was sent, but other emails (not all) from my inbox were included as a thread in that email. There is no way I can do this manually in Hotmail, and I fail to see how a virus or malware on my computer (is it possible?) could start a new process in Hotmail. I have seen this issue mentioned on the internet somewhere, but I cannot remember the exact verbage used in order to find the info. Any suggestions or "cures"?