Mail is not sent by setup of windows Application

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C#3.5

Hello Experts,
I am working on a windows application. I am sending a mail trough gmail on a button at a form. it works fine when I run my application. but if I create Setup of this aapplication then it gives error. How i Solve it .Pls Help

Thanks in advance.....
The error which i got is

The remote certificate is invalid according to the validation procedure.

and my code is

mail.From = new MailAddress("abc@gmail.com");//My Gmail ID
                       string emp = "";
                       mail.To.Add(txtemail.Text);
                       mail.Subject = "Confirmations of User Name && Password";
                       StreamReader reader = new StreamReader("HTMLPage1.htm");
                       string readFile = reader.ReadToEnd();
                       string myString = readFile;
                       string date = System.DateTime.Now.Date.ToShortDateString();
                       string str = PopulateBodyEnquiry(txtCmp.Text, UserName, UserName, Pwd, date);
                       mail.Body = str;
                       mail.IsBodyHtml = true;
                       SmtpClient smtp = new SmtpClient("smtp.gmail.com");
                       smtp.Port = 587;
                       smtp.Host = "smtp.gmail.com";
                       smtp.EnableSsl = true;
                       smtp.UseDefaultCredentials = false;
                       smtp.Credentials = new System.Net.NetworkCredential("mygmailId", "password");
                       smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
                       ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(delegate(object sender2, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
                       {
                           return true;
                       });
                       smtp.Send(mail);