Campaign Email Tracking Gif not showing correctly

Campaign Email Tracking Gif not showing correctly

I have a problem where the email that is sent as part of a campaign has a large empty gif at the bottom of the email. It looks very bad in Apple Mail. Any ideas why the campaign puts this into the page and why it always displays as a large image?

This is the code from the raw source:
<img src=3D"http://zc1.maillist-manage.com/open/od11287eca3dd981_rd1504a948 bf6c12f.gif" height=3D"1" width=3D"320"/>

And this is what the campaign email looks like: