int row2 = e.RowIndex;
        string em = GridView1.Rows[row2].Cells[2].Text;
        MailUtility mu = new MailUtility();
        mu.SendMail(em, "thank you", "thank you");


using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mail;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

/// <summary>
/// Summary description for MailUtility
/// </summary>
public class MailUtility
{

    public void SendMail(string sendTo, string subject, string body)
    {
        MailMessage m = new MailMessage();
        m.From = new MailAddress("BarBichachiSite@gmail.com",
        "אני");
        m.To.Add(new MailAddress(sendTo));
        m.Subject = subject;
        m.Body = body;
        SmtpClient sc = new SmtpClient();
        sc.EnableSsl = true;
        sc.Send(m);
    }





<system.net>
    <mailSettings>
      <smtp>
        <network host="smtp.gmail.com" port="587" userName="BarBichachiSite@gmail.com" password="1234567d" />
      </smtp>
    </mailSettings>
  </system.net>