If you're forwarding the message manually, you can choose to do so by clicking the down arrow by the forward button and choose the forward command. If you just click on the forward but, by default it forwards the message as an attachment.
If you're forwarding via a rule it doesn't appear there is anything in the client to prevent the message from being rule-forwarded as an attachment so you need to add the /flatfwd switch to the GWIA.CFG file and/or select the Flat Forwarding check box on the message handling page of the SMTP/MIME tab in the properties of your GWIA gateway.
Scott
