how to send an email from ASP.Net appliaction

Using system.net.Mail

Enter Email :<asp:textbox id="txtEmail" runat="server" xmlns:asp="#unknown"></asp:textbox><br />
<asp:button id="btnSubmit" runat="server" xmlns:asp="#unknown" />

protected void btnSubmit_Click(object sender, EventArgs e)
    {
String strEmail,strFrom,strTo,strSubject,strBody;
           strEmail= txtEmail.Text.ToString();
           strTo = ConfigurationManager.AppSettings["RequestEmail"].ToString();
           strSubject = "News letter subscription";
           strBody = "Email = "+ strEmail.ToString();
           strEmail = Trim(txtEmail.Text);
           MailMessage objmail=new MailMessage();
           objmail.From = strEmail;
           objmail.To.Add(strTo);
           objmail.Subject = strSubject;
           objmail.Body = strBody;
           objmail.IsBodyHtml = True;
           SmtpMail = new SmtpClient(ConfigurationManager.AppSettings["SmtpServer"].ToString()); 
           SmtpMail.Send(objmail);
    }

//Give the ToEmail address .To which you need to send a mail

<add key="RequestEmail" value="test@maildomain.com" />
//Give the server(domain name) in value

<add key="SmtpServer" value="Smptp server name" />