Using Mailkit : "The SMTP server has unexpectedly disconnected."

Question

I am trying to use a free SMTP relay from SendGrid to send emails from my ASP.NET application. I can connect to the server, but when I try to authenticate, I get this error : "The SMTP server has unexpectedly disconnected."

using (var client = new SmtpClient())
        {
            client.ServerCertificateValidationCallback =
                (sender, certificate, certChainType, errors) => true;
            client.AuthenticationMechanisms.Remove("XOAUTH2");

            // connection
            client.Connect("smtp.host", 465, true);
            client.Authenticate("UserName", "Password");//error occurs here

            client.Send(email);
            client.Disconnect(true);
        }

Once again, I can connect without any problem, but when I try to authenticate, I get the previously mentionned error...

Any suggestions?

Cheers

Answer 1

I solved my issue changing from SendGrid to gooogle's free SMTP service for all of their users. Simply follow the steps here and you should be good to go!