mail is moving to queue folders not to recipiants

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IIS6

C#

ASP.NET

IIS

My problem is SMTP Server (localhost) sends the email but it sits in the Queue folder.

So I see all my emails are in C:\Inetpub\mailroot\Queue

Any Ideas how can I resolve this ,i developed application using asp.net and c#

for sending email applications.i am using iis6.0,window 2008 r2,what r settings requried in smtp


my code is give below can i provide any setting under smtp?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net.Mail;
using System.Web.Mail;
using System.Configuration;

namespace Emailapp
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnclick_Click(object sender, EventArgs e)
        {

                     string strFrom=txtfrom .Text.Trim ();
                     string  strTo = txtTo.Text.Trim();
                     string strCc = txtCc.Text.Trim();
                    string strSubject = txtSubject.Text.Trim();
                    string strBody = txtbody .Text .Trim ();
            SendEmail(strFrom, strTo, strCc, strSubject, strBody);
        }

private void SendEmail(string strFrom, string strTo, string strCc, string strSubject, string strBody)
        {
            try
            {
                System.Net.Mail.SmtpClient  smtp = null;
                System.Net.Mail.MailMessage msg = null;
                smtp = new System.Net.Mail.SmtpClient("smtp.mydomain.com");
                                msg = new System.Net.Mail.MailMessage();
                msg.From = new System.Net.Mail.MailAddress(strFrom);


                #region To
                if (!string.IsNullOrEmpty(strTo.ToString().Trim()))
                {
                    string[] sTo = strTo.ToString().Split(';');
                    for (int i = 0; i < sTo.Length; i++)
                    {
                        if ((sTo[i].ToString().IndexOf('@') != -1) && (sTo[i].ToString().IndexOf('.') != -1))
                            msg.To.Add(new System.Net.Mail.MailAddress(sTo[i].ToString()));
                    }
                }
                #endregion To


                #region Cc
                if (!string.IsNullOrEmpty(strCc.ToString().Trim()))
                {
                    string[] sCc = strCc.ToString().Split(';');
                    for (int i = 0; i < sCc.Length; i++)
                    {
                        if ((sCc[i].ToString().IndexOf('@') != -1) && (sCc[i].ToString().IndexOf('.') != -1))
                            msg.CC.Add(new System.Net.Mail.MailAddress(sCc[i].ToString()));
                    }
                }
                #endregion Cc

                 msg.Subject = strSubject;
                msg.Body = strBody;
                msg.IsBodyHtml = true;
                smtp.Send(msg);
                //SmtpMail.Send(msg);
                 Response.Write("Your Email has been sent sucessfully");



            }
            catch (Exception ee)
            {
              Response .Write ("failour message"+ee.ToString ());
            }
            //catch (SmtpException smEx)
            //{
            //    throw new ArgumentException("Email sending failed with " + smEx.StatusCode.ToString());
            //}
        }
    }


        }