Sending Email in C#

As I said, please "refer to the articles in this web site". Have you looked at the following two?

• Send an Email with attachment from Outlook, Yahoo, Hotmail, AOL and Gmail
• Sending mails with attachments using Gmail

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Net;
using System.Net.Mail;

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

    }
    protected void btnSend_Click(object sender, EventArgs e)
    {
        SmtpClient serverobj = new SmtpClient();
        serverobj.Credentials = new NetworkCredential(txtUserName.Text, txtPassword.Text);
        serverobj.Port = 587;//25 is Default port number for gmail
        serverobj.Host = "smtp.gmail.com";
        serverobj.EnableSsl = false;

        msgobj = new MailMessage();
        msgobj.From = new MailAddress(txtUserName.Text,"MessageName");
        //write here emailid to whom we r sending mail or pass through text box
        msgobj.To.Add("[email protected]");
        msgobj.Subject = "MessageDemo";
        msgobj.Body = "Write here Message Body or Pass through TextBox";
        msgobj.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
        serverobj.Send(msgobj);
    }

    }