I recently ran into an issue where a user had uploaded an Outlook Message file to a web application. The users were reporting an error that each time they tried to click on a link to the .MSG file, the web browser would display an error message that the file had been moved or could not be found. This issue was happening across all web browsers, including Internet Explorer, Chrome, Firefox and Safari.
The web server was running Windows 2008 R2 Service Pack 1.
What I did not realize and was surprising to me was that a Mime Type is not defined by default for .MSG files in IIS, surprising because it is a Microsoft Outlook file extension and a Microsoft web server.
The fix was surprisingly simple. I logged into the web server and opened the IIS Manager.
I selected the Web server and clicked on the Mime Types icon.
Click the Add link and create the following new .msg Mime Type: application/vnd.ms-outlook
This immediately fixed the issue without an IISRESET or server reboot.