Restrict purchases to recipients who opened mail or clicked
The system currently counts all purchases for all email recipients. That overstates the effectiveness of the campaign. It should only count purchases for customers who actually opened their email - or you should at least provide an option to restrict it accordingly.
Steve Baird commented
You should also be able to segment a campaign to a specific item (or item range), category, sub-category or vendor and have the dashboard only report sales from e-mail recipients who purchased from that segment