Unlike inactivating MIME types, deletion is permanent and affects associated items. You cannot import files that have extensions associated with a deleted MIME type.
For items associated with a deleted MIME type, the text “unknown file type” is displayed instead of MIME type icons. When users open these items, they are prompted to select a program executable.
You can delete MIME types that you define; however, you cannot delete built-in EPM Workspace MIME types.