C# Solution of Problem: “The remote certificate is invalid according to the validation procedure.” Posted on September 28, 2017January 8, 2018 by Ibrahim Ersoy Sharing is Caring0sharesFacebook0TwitterGoogle+Pinterest0LinkedIn0While sending email with code,you get this error. Solution is simple! Do not send it with SSL //smtpClient.EnableSsl = true; Comment/Delete this line if you have used.