The problem is here - once again - that Mozilla handles the file correctly, it only looks at it MIME-type. IE also look at the filetype extension which Mozilla completely ignores. There is a bug ...

The plugin additionally allows the mime types and file extensions to WordPress. In other words, your WordPress site can upload various file extensions. About the mime type list, please see the ...

If you are unable to thread MIME ... save the file, delete all text before the email header (The headers including the From and To fields). Now, save the file by adding the .eml file extension ...

Now, type ‘.mp4’ in the ‘File Name Extension’ field. Also, enter ‘video/mp4’ in the ‘MIME Type’ text box. Click the ‘OK’ button.