Outlook/Url issue

Okay...

First off let me start by saying there is Third Party software installed that this company uses for all their database related things.

Sooo...

In a users Outlook there is a .pdf link in some email he recieved. So when this particular user clicks the link, it initiates the workstation installation wizard. Everyone else including me at my office can open it and see the pdf. But when he copies the URL and pastes it in a browser it works fine. Is there anything in Outlook that you might think of that can interfere like this?

Thanks for reading.