.aspx
<%@ Page
Language="C#"
AutoEventWireup="true"
CodeFile="Default2.aspx.cs"
Inherits="Default2"
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD
XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    TO: <asp:TextBox ID="txtto" runat="server"></asp:TextBox>
        <br />
        Sub:
<asp:TextBox ID="txtsub" runat="server"></asp:TextBox>
        <br />
       
Body:<asp:TextBox ID="txtbody"
runat="server"
TextMode="MultiLine"></asp:TextBox>
        <br />
    <asp:Button ID="btnmail"
runat="server"
Text="Send"
onclick="btnmail_Click"
/>
    </div>
    </form>
</body>
</html>
-------------------------------------------------
.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.Mail;
using System.Net.Mail;
public partial class Default2 :
System.Web.UI.Page
{
    string gmailusername = System.Configuration.ConfigurationManager.AppSettings["Gmailusername"].ToString();
    string pwd = System.Configuration.ConfigurationManager.AppSettings["Password"].ToString();
    string port = System.Configuration.ConfigurationManager.AppSettings["Port"].ToString();
    string protocval = System.Configuration.ConfigurationManager.AppSettings["protocal"].ToString();
    protected void
Page_Load(object sender, EventArgs e)
    {
    }
    protected void
btnmail_Click(object sender, EventArgs e)
    {
       
System.Net.Mail.MailMessage newmsg = new System.Net.Mail.MailMessage();
       
newmsg.From = new MailAddress(gmailusername);
           
newmsg.Subject = txtsub.Text;
            newmsg.To.Add(txtto.Text);
           
newmsg.Body = txtbody.Text;
            SmtpClient smtp = new
SmtpClient();
           
smtp.Host = protocval;
           
smtp.Port = Convert.ToInt32(port);
           
smtp.Credentials = new System.Net.NetworkCredential(gmailusername,pwd);
           
smtp.EnableSsl = true;
           
smtp.Send(newmsg);
           
Response.Write("msg is send");
    }
}
===============================================================
Web.config
<?xml version="1.0"?>
<!--
 
For more information on how to configure your ASP.NET application,
please visit
 
http://go.microsoft.com/fwlink/?LinkId=169433
 
-->
<configuration>
 
<connectionStrings>
   
<add name="myconnreader" connectionString="Data Source=KCLINK-PC\SQLEXPRESS;Initial
Catalog=mydataworld;Integrated Security=True"/>
 
</connectionStrings>
 
<appSettings>
   
<add key="Gmailusername" value="x@gmail.com"/>
   
<add key="Password" value="xx"/>
   
<add key="Port" value="587"/>
   
<add key="protocal" value="smtp.gmail.com"/>
 
</appSettings>
     <system.web>
           <compilation debug="true" targetFramework="4.0"/>
     </system.web>
</configuration>
================================================================Note: Where X is Ur USERNAME
Where XX is Ur PASSWORD



