is gmail ?

isgmail.js

function is_gmail(email, callback) {
    var email_host_regex = /.*@(.+)$/;
    var gmail_servers_regex = /(\.google\.com|\.googlemail\.com)$/i;
    var m = email_host_regex.exec(email);
    if(m && m.length > 1) {
        var host = m[1] && m[1].toLowerCase();
        if(host == "gmail.com") {
            return callback(null, true);
        } else {
            dns.resolveMx(host, function(err, result) {
                if(err || !result || result.length === 0) return callback(err, false);
                for(var i=0; i < result.length; i++) {
                    var record = result[i];
                    m = gmail_servers_regex.exec(record.exchange);
                    if(m && m.length > 1) return callback(null, true);
                }
                return callback(null, false);
            });
        }
    } else {
        return callback(null, false);
    }
}

function is_yahoo(email, callback) {
    var email_host_regex = /.*@(.+)$/;
    var yahoo_servers_regex = /(\.yahoodns\.net)$/i;
    var m = email_host_regex.exec(email);
    if(m && m.length > 1) {
        var host = m[1] && m[1].toLowerCase();
        if(host.match(/yahoo\.[a-z]{2,3}$/i)) {
            return callback(null, true);
        } else {
            dns.resolveMx(host, function(err, result) {
                if(err || !result || result.length === 0) return callback(err, false);
                for(var i=0; i < result.length; i++) {
                    var record = result[i];
                    m = yahoo_servers_regex.exec(record.exchange);
                    if(m && m.length > 1) return callback(null, true);
                }
                return callback(null, false);
            });
        }
    } else {
        return callback(null, false);
    }
}