Or EML/MHT. It's the format the email programs use to store the HTML mail incl all pictures, JS, CSS, ... in one plain text file. IE 9-11 also supports that for

Or EML/MHT. It's the format the email programs use to store the HTML mail incl all pictures, JS, CSS, ... in one plain text file. IE 9-11 also supports that format (file -> save as...) but calls it MHT?