my emails are being linked together

I received emails from a few different companies. One email was in the junk folder and I marked it as not junk. After that I could not find it for some time and when I did it was linked to four other separate emails. When I scroll down all the emails from different senders are all showing but I replied to them individually and I do not want replies to these companies going to the wrong senders or all the emails linked in one. I have no idea how this happened but I am very angry. Ever since hotmail was switched to outlook I have been having issued with my email service.