Apple email account receiving another account's emails

Several years ago I had set up my outlook account e-mails to also be received on my me.com account. Now I want to end this but I can't recall or figure out how. The e-mails to my apple account are not being forwarded but actually being received directly into my mail account as if it had been sent directly. When you view the "To" address it is the Outlook account address. I have viewed preferences in my Apple Account and the only accounts listed there are the me.com and the icloud.com address. I have also looked into my Rules folder of Outlook and there are none recorded. If anyone has any idea of how to stop this your response would be appreciated.