Ok, I realized now that there should be google analytics tracking. We just sent out 9087 emails using Winback and it had index&1 in all of the emails instead of the tracking, even though all of that is configured properly.

Here is a hint to help you find the bug, on another website, I downloaded the version from Zen Cart downloads section first and then upgraded to 1.7 on top of that after receiving the notification in the Mailbeez admin. In that installation, the tracking info works properly.

In the installation where we installed the version from your site right off the bat, we get the &1 problem...