Thanks for the rely. I tried that and the issue doesn’t seem to be going away. I think I have found a solution though. The problem is the template container table has a max-width: 600px !important rule which outlook 2003 doesn’t seem to follow. I have fixed this by exporting my campaign as an HTML file, adding width: 600px to the template container table and copy/pasting the template into mailchimp. This seems to have fixed the issue.
I do lose the ability to customize blocks within the mailchimp interface after doing this though, which is unfortunate. I can however set everything up before hand and fix this bug lastly.
Thanks for your help!