GMail is making a lot of changes lately... wouldn't it be nice to know who - other than those with a gmail.com email address - are using GMail and help them ensure they continue to get your emails? Here's one way using JavaScript and node.js.

checkgmail.js

// written to run in the console
// using node.js
// by a non-programmer... no warranties here.
// Use at your own risk!
// http://twitter.com/lincolnmurphy
// I probably can't help you with programming issues,
// but feel free to follow me

var dns = require('dns'), 
  fs = require('fs');

// I used a file in the same directory as the script
// each line has one email address and that's all
// no commas, tabs etc.
// make sure there are no headers (if you copy from a CSV or Excel this might happen)
// and ensure there aren't any extra blank lines at the bottom
// or modify the script to deal with those issues... 
var path = "email.txt";
var emails = fs.readFileSync(path).toString().split('\n'); //synchronous

// if an email has a domain from one of these
// they are obviously not GMail so we don't care
// Also, if they have gmail.com as their email address,
// you don't need to run them through this script... :-)
// these are the most common non-GMail public email system domains
// on my list... you may find others
var excludeDomains = [
	'gmail.com', 
	'yahoo.com', 
	'googlemail.com', 
	'live.com',
	'outlook.com',
	'hotmail.com',
	'rocketmail.com',
	'me.com',
	'att.net',
	'yahoo.ca']

	
//console.log("we're going to check this many emails: " + emails.length);

for(var o=0;o<emails.length;o++){
	var iEmail = emails[o];
//	console.log(iEmail);
	
	var iDomain = emails[o].replace(/.*@/, "");
//	console.log(iDomain);

// most GMail MX records have either or both of these domains
// I just looked throught he JSON object as a string for those
// no need to get fancy; if one of those is there, they're on GMail
// though you can get as fancy as you want
	var mxValue = 'google.com'; 
	var mxValueTwo = 'googlemail.com';
	var goodToGo = "yes"
		
	for(var e=0;e<excludeDomains.length;e++){
			console.log("the current domain is " + iDomain + " and the excluded domain is " + excludeDomains[e]);
		if(iDomain === excludeDomains[e]){
			goodToGo = "no";
		}
				
	}
  // if the domain is not on our excluded list
  // do the lookup (this happens behind the scenes)
  // kinda cool node.js stuff going on here, BTW
		if(goodToGo === 'yes'){
			doLookup(iDomain, iEmail);
		}

}

	console.log("it's running in the background... asynchronously");


    // in the same directory as this script
    // I created a file called results.txt
    // it just writes a new line to the file
    // every time there's a result or an error
    // it writes the email address, a tab, then the result
    // this will allow you to easily copy and paste into
    // Excel or a Google Spreadsheet
    // You could output to a web page or dump to Google Drive via API
    // I took the easy way out
    // oh, and the error handling is 'dumb'
    // it just writes that there was an error - likely a timeout -
    // so you can put those email addresses back in the
    // source file and try again.
function doLookup(dDomain, dEmail) {
		dns.resolveMx(dDomain, function (err, addresses) {
		if (err) {
			fs.appendFile('results.txt', dEmail + "\t'Error'\n", function (err) {
				});
				return(null);
		}
		
		var stAttrValue = JSON.stringify(addresses);
		var stLcAttrValue = stAttrValue.toLowerCase();
    
		if (stLcAttrValue.indexOf(mxValue) !== -1 || stLcAttrValue.indexOf(mxValueTwo) !== -1){
			fs.appendFile('results.txt', dEmail + "\tY\n", function (err) {
			});
		}		
		else {
			fs.appendFile('results.txt', dEmail + "\tN\n", function (err) {
			});
		}
		});

}