Thank you for your past order to AccessoryGenie.com. As our way of saying Thank You we have a ** GREAT LABOR DAY SPECIAL***
Any one of those lines "Thank you for your PAST order", "Our way of saying thank you", "GREAT LABOR DAY SPECIAL", "ENLARGE Y@UR M@RT6A6E", etc etc, would have been fine subject lines, and I never would have brought it up.
Well, maybe if they had said something Yoda-like, such as "For Your Order, You, I Thank". I would have definitely brought that up, but in a good way. See AccGenie? See what you've lost? But I forgive you: "Thank you for my material".