How do we prevent Outlook from giving a warning dialog for every email?
This is related to a security update that was part of Windows XP Service Pack 2 and there is no direct way to shut it off within Windows. However, there is a small utility called ClickYes by Context Magic which appears to solve the issue. A free version is available along with a paid version with additional features. Pricing, a feature comparison chart and download links are at the end of the page.