[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Index(EmailFormModel model, IEnumerable<HttpPostedFileBase> files)
{
    if (ModelState.IsValid)
    {

        List<string> paths = new List<string>();

        foreach (var file in files)
        {
            if (file.ContentLength > 0)
            {
                var fileName = Path.GetFileName(file.FileName);
                var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
                file.SaveAs(path);
                paths.Add(path);
            }
        }

            var message = new MailMessage();
            foreach (var path in paths)
            {
                var fileInfo = new FileInfo(path);
                var memoryStream = new MemoryStream();
                using (var stream = fileInfo.OpenRead())
                {
                    stream.CopyTo(memoryStream);
                }
                memoryStream.Position = 0;
                string fileName = fileInfo.Name;
                message.Attachments.Add(new Attachment(memoryStream, fileName));
            }

            //Rest of business logic here
            string EncodedResponse = Request.Form["g-Recaptcha-Response"];
            bool IsCaptchaValid = (ReCaptcha.Validate(EncodedResponse) == "True" ? true : false);
            if (IsCaptchaValid)
            {

                var body = "<p>Email From: {0} ({1})</p><p>Subject: {2} </p><p>Message:</p><p>{3}</p>";
                message.To.Add(new MailAddress("***@gmail.com"));  // replace with valid value
                message.From = new MailAddress("***@ymailcom");  // replace with valid value
                message.Subject = "Your email subject";
                message.Body = string.Format(body, model.FromName, model.FromEmail, model.FromSubject, model.Message);
                message.IsBodyHtml = true;
                using (var smtp = new SmtpClient())
                {
                    var credential = new NetworkCredential
                    {
                        UserName = "***@gmail.com",  // replace with valid value
                        Password = "***"  // replace with valid value
                    };
                    smtp.Credentials = credential;
                    smtp.Host = "smtp.gmail.com";
                    smtp.Port = 587;
                    smtp.EnableSsl = true;
                    await smtp.SendMailAsync(message);
                    ViewBag.Message = "Your message has been sent!";

                    ModelState.Clear();
                    return View("Index");
                }

            }
            else
            {
                TempData["recaptcha"] = "Please verify that you are not a robot!";
            }
        }return View(model);


    }

public class ReCaptcha
    {
        private string m_Success;
        [JsonProperty("success")]

        public string Success
        {
            get { return m_Success; }
            set { m_Success = value;}
        }
        private List<string> m_ErrorCodes;
        [JsonProperty("error-codes")]

        public List<string> ErrorCodes
        {
            get { return m_ErrorCodes; }
            set { m_ErrorCodes = value; }
        }

        public static string Validate(string EncodedResponse)
        {
            var client = new System.Net.WebClient();
            string PrivateKey = "***";
            var reply = client.DownloadString(string.Format("https://www.google.com/recaptcha/api/siteverify?secret={0}&response={1}", PrivateKey, EncodedResponse));
            var captchaResponse = JsonConvert.DeserializeObject<ReCaptcha>(reply);
            return captchaResponse.Success;
        }
    }