C# – Want to send automatic mail from asp.net website

I am trying to send an automatic mail from my asp.net website whenever a person will click submit button to enter some value. I have created some codes in C#. It's not showing any error, but also not sending any mail. I am using ip address of the mail server of the organization in the network credential. I am not sure how to provide password for the email address I am using to send mail. I am sharing my code with you.

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.ComponentModel;// for backgroundworker class
using System.Net;
using System.Net.Mail;
using System.Threading;

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

    }

    protected void LoginView1_ViewChanged(object sender, EventArgs e)
    {

    }

    public void Button3_Click(object sender, EventArgs e)
    {
        using (SqlConnection connn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
        {

            SqlCommand command = new SqlCommand();
            command.CommandType = System.Data.CommandType.StoredProcedure;
            command.CommandText = "dbo.Procedure";

            command.Parameters.Add("@name", System.Data.SqlDbType.VarChar).Value = TextBox1.Text;
            command.Parameters.Add("email", System.Data.SqlDbType.VarChar).Value = email.Text;
            command.Parameters.Add("sub", System.Data.SqlDbType.VarChar).Value = sub.Text;
            command.Parameters.Add("message", System.Data.SqlDbType.VarChar).Value = message.Text;

            string from = "info@xxx.com";
            string to = "abc@xxx.com";
            string mailSubject = sub.Text.ToString();
            string mailBody = message.Text.ToString(); 
            MailMessage mess = new MailMessage(from, to, mailSubject, mailBody);
            mess.IsBodyHtml = true;
            SmtpClient emailClient = new SmtpClient("//xxx.xxx.x.x/", 25); //Server ip & port
            emailClient.UseDefaultCredentials = true;
            //System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential("", "");
            //emailClient.Credentials = SMTPUserInfo;
            //emailClient.Send(mess);

           // emailClient.Credentials = CredentialCache.DefaultNetworkCredentials;

            try
            {
                emailClient.Send(mess);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception caught in CreateTestMessage1(): {0}",
                      ex.ToString());
            }

            command.Connection = connn;
            connn.Open();
            command.ExecuteNonQuery();
            connn.Close();
        }
        TextBox1.Text = "";
        email.Text = "";
        sub.Text = "";
        message.Text = "";
        lblmsg.Text = "Data entered successfully!!! Thank You for contacting us! We will get back to you as soon as possible.";
        //Response.Write("Submitted Succesfully");
        Response.Redirect("~/XX.aspx");
    }
}