Render mhtml document

Hello everyone,
I am facing issues in rendering mhtml content on a browser or even not able to open it with file-opener plugin after saving it to a .mht file.

Actually the content is in base64 format first I am decoding it to UTF8 and saving it as .mht file using file plugin but I am not sure about the mime type I used multipart/related, message/rfc822 and application/x-mimearchieve, the file was saved successfully but when I tried to render it to inAppBrowser or tried to open it via file-opener plugin its not opening.
Can anyone guide me through this.