Below is sample code showing how to send email from ASP.Net 4 (currently in beta as of this posting) using C#. With this code I am assuming that the server already has a local SMTP service installed, so I use "localhost" to relay the email.

Here is the SendMail.aspx page:

<%@ 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></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        Message to:
        <asp:TextBox ID="txtTo" runat="server"></asp:TextBox>
        <br />
        Message from:
        <asp:TextBox ID="txtFrom" runat="server"></asp:TextBox>
        <br />
        Subject:
        <asp:TextBox ID="txtSubject" runat="server"></asp:TextBox>
        <br />
        Message Body:
        <br />
        <asp:TextBox ID="txtBody" runat="server" Height="171px" TextMode="MultiLine"
            Width="270px"></asp:TextBox>
        <br />
        <asp:Button ID="Btn_SendMail" runat="server" onclick="Btn_SendMail_Click"
            Text="Send Email" />
        <br />
        <br />
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
    </div>
    </form>
</body>
</html>

Here is the source code of the SendMail.aspx.cs page:

using System;
using System.Web.UI.WebControls;
using System.Net.Mail;


public partial class SendMail : System.Web.UI.Page

{
    protected void Btn_SendMail_Click(object sender, EventArgs e)
    {
        MailMessage mailObj = new MailMessage(
            txtFrom.Text, txtTo.Text, txtSubject.Text, txtBody.Text);
        SmtpClient SMTPServer = new SmtpClient("localhost");
        try
        {
           SMTPServer.Send(mailObj);
        }
            catch (Exception ex)
        {
            Label1.Text = ex.ToString();
        }
    }
}

Hope this tutorial can help!!