It looks like a recent Windows Security Update has created extra security, which causes problems when trying to open attachments in your e-mail. Here is the best way to allow attachments to save in the proper format with Web Outlook. This is a one time setting change according to Thomas R:
In your internet browser, get to your Webmail login page. In the top, righthand corner of the screen, click on Tools > Internet Options > Security. Click "Trusted Sites" and then on the "Sites" button (circled in red above).
The Webmail sign in address should appear. Click "Add" to add this site to the list of trusted sites.
