Your welcome. dangrossman answered this in detail already and I agree with what he says. Just as an example, in my system each email that gets sent out has a

Your welcome. dangrossman answered this in detail already and I agree with what he says. Just as an example, in my system each email that gets sent out has a unique id (in our case a hashed id), we use that as the id value. From there we can get back to campaign, email address, company etc. As for the image itself, it is physically only one image generally (or an image byte stream cached in RAM). btw -- dangrossman used sequential numbers as the ID only as an example to show you, you wouldn't do that in a production system. Have fun!