Check this post also for sending mails with dynamic content Send Templated Emails Using MailDefinition Object in asp.net

Sending Emails from asp.net application using c#.net 

Check this post also for sending mails with dynamic content Send Templated Emails Using MailDefinition Object in asp.net

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


    public partial class Default5 : System.Web.UI.Page
    {


        protected void btEnvoyer_Click(object sender, EventArgs e)
        {
            MailMessage message = new MailMessage();
            SmtpClient smtpClient = new SmtpClient();

   //         try
 //          {
                MailAddress fromAddress = new MailAddress(tbDestinataire.Text);
                message.From = fromAddress;
                message.To.Add(tbDestinataire.Text);
                message.Subject = tbObjet.Text;
                message.IsBodyHtml = true;
                message.Body = tbMessage.Text;
                // We use gmail as our smtp client
                if (LstMail.Text == "@yahoo.fr")
                {
                    smtpClient.Host = "smtp.mail.yahoo.com";
                    smtpClient.Port = 25;
                    smtpClient.EnableSsl = false;
                }
                if (LstMail.Text == "@gmail.com")
                {
                    smtpClient.Host = "smtp.gmail.com";
                    smtpClient.Port = 587;
                    smtpClient.EnableSsl = true;
                }


//                smtpClient.UseDefaultCredentials = true;
                smtpClient.Credentials = new System.Net.NetworkCredential(tbExpediteur.Text, tbPassword.Text);

                smtpClient.Send(message);
//            }
//            catch
//            {

//            }

        }

        }