gistfile1.js

function check(host, callback){
	var dns = require('dns');
	var net = require('net');

	var blacklist = ['72.51.33.80'];

	function resolved(err, ip){
		callback(!err && blacklist.indexOf(ip) !== -1);
	}

	dns.resolveMx(host, function(err, results){
		if (err) return callback(err);
		var exchange = results[0].exchange;
		if (net.isIP(exchange)) {
			resolved(null, exchange);
		} else {
			dns.resolve(exchange, function(err, results){
				resolved(err, results[0]);
			});
		}
	});
}

var time = Date.now();
check('mailinator.com', function(result){
	console.log('blacklisted:', result);
	console.log('took:', (Date.now() - time) + 'ms');
});