problem sending email through asp.net

 i m trying to send email through asp.net application but something goes wrong . so pls help me in this regard
 
code is bellow
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<%@ Page Language="C#" AutoEventWireup="true" CodeFile="SendMail.aspx.cs" Inherits="SendMail" %>

<!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>Untitled Page</title>
    <style type="text/css">
        .style1
        {
            width: 100%;
            bo ...