Using MAPI in VB

I am using MAPI to auto send email in a VB app. This all works fine, but a copy of each email sent is stored in the Sent Items folder. This occurs even if the option is disabled in Outlook. It appears that MAPI is bypassing the Outlook options and there does not seem to be a property in the MAPI control that can disables this facility. Does anyone know of a way of stopping copies of emails appearing in Sent Items through the MAPI controls?

Note: before anyone suggests it, using Winsock is not an option.