ASP.net MVC 5 project SMTP function error [duplicate]

As the title above, I have created a project with simple log-in and registration. Inside the program, I have use System.Net.Mail.SmtpException to send the email verification to the user email. I have done created the email but when I click on create a new account, I met this problem as well.

System.Net.Mail.SmtpException: 'The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required

From the information I search, I found out someone say I need to make my email 2-step verification. I did it but the problem still there.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Mail;
using System.Web;
using System.Web.Mvc;
using Food_Founder.Models;

namespace Food_Founder.Controllers
{
    public class UserController : Controller
    {
        //Registration
        [HttpGet]
        public ActionResult Registration()
        {
            return View();
        }

        //Post Registration
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Registration([Bind(Exclude = "IsEmailVerified,ActivationCode")]User user)
        {
            //Model Validation
            bool Status = false;
            string message = "";

            //Email is already exist
            if (ModelState.IsValid)
            {
                #region Email is already exist
                var isExist = IsEmailExist(user.Email);
                if (isExist)
                {
                    ModelState.AddModelError("EmailExist", "Email already exist");
                    return View(user);
                }
                #endregion

                #region Generate Activation Code
                user.ActivationCode = Guid.NewGuid();
                #endregion

                #region Password Hashing
                user.Password = Crypto.Hash(user.Password);
                user.ConfirmPassword = Crypto.Hash(user.ConfirmPassword);
                #endregion

                user.IsEmailVerified = false;

                #region Save Data to Database
                using (myDatabaseEntities myDatabase = new myDatabaseEntities())
                {
                    myDatabase.Users.Add(user);
                    myDatabase.SaveChanges();

                    //Send Email to User
                    SendVerificationLinkEmail(user.Email, user.ActivationCode.ToString());
                    message = "Registration successfully done. Account activation link" +
                        "has been send to your Email:" + user.Email + "Please go check and activate your account";
                    Status = true;
                }
                #endregion

            }
            else
            {
                message = "Invalid Request";
            }

            ViewBag.Message = message;
            ViewBag.Status = Status;
            return View(user);
        }

        //Verify Email


        //Verify Email Link


        //Login


        //Login POST


        //Logout



        [NonAction]
        public Boolean IsEmailExist(string email)
        {
            using (myDatabaseEntities myDatabase = new myDatabaseEntities())
            {
                var v = myDatabase.Users.Where(a => a.Email == email).FirstOrDefault();
                return v != null;
            }
        }

        [NonAction]
        public void SendVerificationLinkEmail(string email, string activationCode)
        {
            var verifyUrl = "/User/VerifyAccount/" + activationCode;
            var link = Request.Url.AbsoluteUri.Replace(Request.Url.PathAndQuery, verifyUrl);

            var fromEmail = new MailAddress("[email protected]", "yukwokyao");
            var toEmail = new MailAddress(email);
            var fromEmailPassword = "********";
            string subject = "Your account is successfully created!";

            string body = "<br/><br/>We are excited to tell you that your FoodFounder account is" +
                "successfully created. Please click the below link to verify your FoodFounder account" +
                "<a href = '" + link + "' >" + link + "</a>";

            var smtp = new SmtpClient
            {
                Host = "smtp.gmail.com",
                Port = 587,
                EnableSsl = true,
                DeliveryMethod = SmtpDeliveryMethod.Network,
                UseDefaultCredentials = false,
                Credentials = new NetworkCredential(fromEmail.Address, fromEmailPassword)
            };

            using (var message = new MailMessage(fromEmail, toEmail)
            {
                Subject = subject,
                Body = body,
                IsBodyHtml = true
            })
            smtp.Send(message);
        }
    }
}

The code above is the controller class I created. The problem I found is there so that I didn't put any other design html code in here. The most weird part is even I met this problem, the data I register still can key-in into the database but this annoying problem still exist there. Anywhere, if anything I miss put, please inform me ya.. Thank you.