Notes about the MP21 file extension:
To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened
" (Windows 7) or "How do you want to open this file?
" (Windows 10) if you double-click the file. There click on "More apps"
and choose a suitable software to view such files on your PC or from email attachments.
The MP21 file type is primarily associated with 'AXMEDIS' by AxMediaTech S.R.L.. AXMEDIS tools for content processing can work with any file (audio, video, images, document, animations, HTML, SMIL, MPEG4, OMA, MXF, etc.). It can also produce MPEG-21; when an object is an MPEG-21 package it has more information of a single image or document, and as cons lost its identity in terms of simple file format. A player is available on the AXMEDIS site.
Detailed information for file extension MP21:
Mime type: application/AXMEDIS-object
To change file associations press Windows Key
and then Apps and Features
> Default apps
> Choose default apps by file type
Invalid file associations could be the result of underlying issues within your Windows PC.