I am using Windows 8 and Windows Live Mail on desktop view to access my emails. I have two email accounts, a Hotmail one and a Btinternet account. I am receiving emails to both accounts appropriately but about 5 minutes after an email correctly arrives in my Btinternet account a duplicate copy appears in my Hotmail account. Why is a duplicate being forwarded to my Hotmail account and how do I stop this happening? I can't work out if it is a problem with Hotmail, Windows Live Mail or with Btinternet.

Thanks for your help