Why do my messages keep redownloading even after being read/deleted?

I've had my mac for about two weeks, my Mail has been continually redownloading all the messages in my Hotmail account over and over. I have 2 accounts on Mail, but it is only happening to one, annoyingly the one I use most often!

Can anyone help solve the problem? I haven't been able to understand answers I have found, I'm not too tech savvy...