As a store owner and customer of constant contact I noticed your recent commercials on TV that mention
"Oh and I can even see who opens it".
As a retailer I don't want my customers to start feeling self conscious about whether they open my emails knowing that I'm going to know. It's more professional if my customers don't think about or aren't aware that I can see whether they open it or not.
Respectfully, the commercial has a bit of a "silly" tone which isn't really in keeping with the professionalism of your platform and the tone I would like to maintain with my customers..