I've written a newsletter control panel in PHP and a few thousand emails are sent every month from it. The control panel shows if an email was opened, what date/time and what link was clicked. The open date and time are done using the 1 pixel image trick.
I'm wondering if it's possible to show the number of times a particular email has been opened. Obviously when it's opened the first time, I'm capturing that information. But if the person saves the email with the downloaded images, how would I see if they've opened it again?
Thanks in advance