According to the official requirements, the application is not specifically developed to run on Windows 7. It's compatible with: Windows 98, Me, 2000, and XP. In Windows 7 you have the possibility to apply a Compatibility tweak for the application and in most of the 90 % cases it will work. But you will have to buy the new version from the official website. Yes, the application will work with the compatibility settings applied.
Official website: http://www.avanquestusa.com/products/mysoftware/my_mail_dlx_sys_req.asp