Given a raw mail content `mail.raw`, this decodes and extracts the html part and writes it into `mail.output.html`.

package.json

{
  "name": "extract-html-from-raw-mail",
  "version": "1.0.0",
  "main": "parse.js",
  "dependencies": {
    "mailparser": "~0.4.1"
  },
  "author": "knalli <knallisworld@googlemail.com>",
  "license": "MIT"
}

parse.js

var MailParser = require("mailparser").MailParser;
var mailparser = new MailParser();
var FS = require('fs');
FS.readFile('./mail.raw', function (err, data) {
	if (err) {
		console.error("Failed read: " + err.message);
		return;
	}
	var email = data;
	mailparser.on("end", function(mail_object){
	    FS.writeFile('./mail.output.html', mail_object.html, function (err) {
	    	if (err) {
	    		console.error("Failed write: " + err.message);
	    	}
	    });
	});
	mailparser.write(email);
	mailparser.end();
});