protected void
Button3_Click(object sender, EventArgs e)

    {

        String to = "Tomailid@gmail.com";

        SmtpClient SmtpServer = new
SmtpClient();

String message="your message in body";

       
SmtpServer.Credentials = new System.Net.NetworkCredential("yourmailid@gmail.com
", "password");

       
SmtpServer.Port = 587;

       
SmtpServer.Host = "smtp.gmail.com";

       
SmtpServer.EnableSsl = true;

        MailMessage mail = new
MailMessage();

        try

        {

           
mail.From = new MailAddress("yourmailid@gmail.com", "Subject", System.Text.Encoding.UTF8);

           // mail.To.Add(new MailAddress(to));

           
mail.To.Add(new MailAddress(t));

            // mail.Subject = subject;

           
mail.Body = message;

           
mail.IsBodyHtml = true;

           
mail.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;

           
SmtpServer.Send(mail);

        }

        catch (Exception
err)

        {

        }

    }