Sending mail from website

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net.Mail;

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

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        try
        {            
                    sendmail();
                    Page.ClientScript.RegisterStartupScript(typeof(Page), "alert", "<script language=JavaScript>alert('Query sent successfully.');</script>");
                    TextBox1.Text = "";
                    TextBox2.Text = "";
                    TextBox3.Text = "";
                    TextBox4.Text = "";                
        }
        catch(Exception)
        {

        }
    }

    void sendmail()
    {
        string mail_text = TextBox3.Text + "\n\nFrom: " + TextBox1.Text + "\n\nE-Mail: " + TextBox2.Text;
        MailMessage message = new MailMessage("id@gmail.com", "id@gmail.com", TextBox4.Text, mail_text);
        SmtpClient clnt = new SmtpClient();
        clnt.Port = 587;
        clnt.Host = "smtp.gmail.com";
        clnt.Credentials = new System.Net.NetworkCredential("id@gmail.com", "password");
        clnt.EnableSsl = true;
        clnt.Send(message);
    }
}