Finding difficulty with sending mail after registration

protected void btnSave_Click(object sender, EventArgs e)
{

    HttpCookie cookie = Request.Cookies.Get("Location");
    string Location = string.Empty;
    SqlConnection cn = new SqlConnection(sc);
    SqlCommand cmd = new SqlCommand();
    Location = cookie.Value;

    if (CheckBox1.Checked)
    {


        string sqlstatment = @"INSERT INTO UserInfo (UID, FN, LN, Password, RePass, Email,Country, State,City, Post, Img, Logo,RegDate,Address, UsrType,BizCateg,BizSubCateg) VALUES
        (@UID,@FN,@LN,@Password,@RePass,@Email,@Country,@State,@City,@Post,@Img,@Logo,@RegDate,@Address,@UsrType,@BizCateg,@BizSubCateg)";

        cmd.Connection = cn;
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = sqlstatment;

        //Insert the parameters first
        cmd.Parameters.AddWithValue("@UID", UsrNme.Text);
        cmd.Parameters.AddWithValue("@FN", fnbox.Text);
        cmd.Parameters.AddWithValue("@LN", lnamebox.Text);
        cmd.Parameters.AddWithValue("@Password", passtxtbx1.Text);
        cmd.Parameters.AddWithValue("@RePass", passtxtbx2.Text);
        cmd.Parameters.AddWithValue("@Email", emailbox.Text);
        cmd.Parameters.AddWithValue("@Country", cookie.Value);
        cmd.Parameters.AddWithValue("@State", statedrdolst.SelectedItem.Text);
        cmd.Parameters.AddWithValue("@City", citiesdrdolst.SelectedItem.Text);
        cmd.Parameters.AddWithValue("@Post", postbox.Text);

        cmd.Parameters.AddWithValue("@Logo", logoFileUpload.FileName);
        cmd.Parameters.AddWithValue("@Address", regaddrstxtbx.Text);
        cmd.Parameters.AddWithValue("@UsrType", UsrTypeDrDo.SelectedItem.Text);
        //cmd.Parameters.AddWithValue("@BizCateg", BizCateDDL.SelectedItem.Text);
        //cmd.Parameters.AddWithValue("@BizSubCateg", SubCatBizDDL.SelectedItem.Text);


        if (BizCateDDL.SelectedIndex < 0)
            cmd.Parameters.AddWithValue("@BizCateg", DBNull.Value);
        else
            cmd.Parameters.AddWithValue("@BizCateg", BizCateDDL.SelectedItem.Value);


        if (SubCatBizDDL.SelectedIndex < 0)
            cmd.Parameters.AddWithValue("@BizSubCateg", DBNull.Value);
        else
            cmd.Parameters.AddWithValue("@BizSubCateg", SubCatBizDDL.SelectedItem.Value);

        cmd.Parameters.AddWithValue("@RegDate", DateTime.Now);



        if (!string.IsNullOrEmpty(UsrNme.Text))
        {
            Lblcheckusername.Text = "User Name Already Exist";
            Lblcheckusername.ForeColor = System.Drawing.Color.Red;
        }
        else
        {
            Lblcheckusername.Text = "User Name Available";
            Lblcheckusername.ForeColor = System.Drawing.Color.Green;
        }

        string imgnouser = "/images/general/nouser.jpg";
        if (persimgFileUpload1.HasFile)
        {
            cmd.Parameters.AddWithValue("@Img", persimgFileUpload1.FileName);
            persimgFileUpload1.SaveAs(Server.MapPath("~/images/users/" + persimgFileUpload1.FileName));

        }
        else
        {

            cmd.Parameters.AddWithValue("@Img", imgnouser);

        }


        if (logoFileUpload.HasFile)
        {

            logoFileUpload.SaveAs(Server.MapPath("~/images/Logos/" + logoFileUpload.FileName));

        }

        SqlDataAdapter ad = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        ad.SelectCommand = cmd;
        ad.Fill(ds);
        Session["UsrNme"] = UsrNme.Text;


        const string username = "admin@gmail.com";

        const string password = "admin111";
        SmtpClient smtpclient = new SmtpClient();
        System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();

        MailAddress fromaddress = new MailAddress("admin@gmail.com");

        smtpclient.Host = "smtp.gmail.com";

        smtpclient.Port = 587;
        mail.From = fromaddress;

        mail.To.Add(emailbox.Text);

        mail.Subject = ("Test Subject");
        mail.IsBodyHtml = true;

        mail.Body = "This is test Mail";
        smtpclient.DeliveryMethod = SmtpDeliveryMethod.Network;
        smtpclient.Credentials = new System.Net.NetworkCredential(username, password);
        try
        {

            smtpclient.Send(mail);
            Response.Write("Email Has been sent successfully.");
        }
        catch (Exception ex)
        {

            Response.Write(ex.Message);
        }


        Response.Redirect("User panel.aspx");
        }

        else
        {
        Label1.Text = "please check the box to continue";
        }

}