Imap help`

I’m using Outlook 2003. I’ve set up an IMAP account with an email address on my domain. When replying to emails the reply goes to that person and to my INBOX! What have I done wrong. This just happened out of no where. When I go into my control panel I see how I’ve set up forwarding to an external address. Webmail doesn’t do this so I am assuming it is an Outlook setting. Nothing else seems to look wrong in the panel or Outlook. Any help would be great!!!