Dyarwood,
I believe that using a Outlook mailbox, is not he correct solution. We are using two different mailbox's in our system, one at our Van, and one that we purchased from our EDI software vendor, that we have suppliers log into to send, and receive data.
If your trading partner were to send the data via the internet, in an email, maybe Outlook could work, but I doubt that this is what they are looking for.