What is error in this. Mail is not Sending to register mail id.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;
using System.Text;
using System.Net;
using System.Net.Mail;

namespace logindemo
{
    public partial class Register : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnRegister_Click(object sender, EventArgs e)
        {
            string connetionString = "Data Source=INFND-DTP-0493;Initial Catalog=Test_DB;User ID=#####;Password=#####";
            SqlConnection conn = new
            SqlConnection(connetionString);
            conn.Open();
            string commText = "select * from login where user_name='"+txtUserName.Text.Trim()+"' or email_id= '" + txtEmailId.Text.Trim() +"' or phone_no=" + Convert.ToDouble(txtPhoneNo.Text) ;
            SqlCommand cmd = new
            SqlCommand(commText, conn);
            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.HasRows)
            {
                Label1.Text = "Duplicte of Data";
            }
            else
            {
            conn.Close();
            MailMessage msg;
            string commText1 = "insert into login(User_Name,Password,Address,City,State,PIN,Phone_no,Email_id,Created_By,Created_on) values('" + txtUserName.Text + "','" + txtPassword.Text + "','" + txtAddress.Text + "','" + txtCity.Text + "','" + txtState.Text + "','" + Convert.ToDouble(txtPin.Text) + "','" + Convert.ToDouble(txtPhoneNo.Text) + "','" + txtEmailId.Text +  "','" + "Alok" + "','" + DateTime.Now + "')";
            SqlCommand cmd1 = new 
            SqlCommand(commText1, conn);
            conn.Open();
            int no = cmd1.ExecuteNonQuery();
            conn.Close();
            if(no>0)
             {
            Label1.Text= "User registration sucessfully";
            System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();
            mail.To.Add(txtEmailId.Text.Trim());
            mail.From = new MailAddress("alokparhi06@gmail.com");
            mail.Subject = "Regarding: Registration conformation";
            mail.Body = "Hi"+txtUserName.Text.Trim()+", You have registered successfully...";
            mail.IsBodyHtml = true;
            SmtpClient client = new SmtpClient();
            client.Credentials = new System.Net.NetworkCredential("alokparhi06@gmail.com", "xyz");
            client.Port = 587;
            client.Host = "smtp.gmail.com";
            client.EnableSsl = true;
            try
              {
            client.Send(mail);

              }
            catch
              {
            Label1.Text="There is some problem while sending Message... ";	
              }



              }
            else
               {
           Label1.Text="Error";
               }
                
            }
        }
    }
}