All email goes to your OWA 1st regardless, when you log into your WIndows Mail, that then connects to the BT mail server and downloads them off of there, which removes it from OWA. You could have the best of both worlds by simply telling Windows Mail to leave a copy of the mail on the mailserver... that way you'll download it to your PC, but still be able to access them via OWA as well. Go to Tools> Accounts> Highlight your mail account and select Properties. Go to the Advanced tab and at the bottom will be the option Leave a copy of the message on the server.