C# Send Email With MailKit

mailkit_example.cs

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var message = new MimeMessage();
            var bodyBuilder = new BodyBuilder();
            
            // from
            message.From.Add(new MailboxAddress("from_name", "from_email@example.com"));
            // to
            message.To.Add(new MailboxAddress("to_name", "to_email@example.com"));
            // reply to
            message.ReplyTo.Add(new MailboxAddress("reply_name", "reply_email@example.com"));

            message.Subject = "subject";
            bodyBuilder.HtmlBody = "html body";
            message.Body = bodyBuilder.ToMessageBody();

            var client = new SmtpClient();

            client.ServerCertificateValidationCallback = (s, c, h, e) => true;
            client.Connect("MAIL_SERVER", 465, SecureSocketOptions.SslOnConnect);
            client.Authenticate("USERNAME", "PASSWORD");
            client.Send(message);
            client.Disconnect(true);
        }
    }
}

A very simple and a crisp example.
Thanks a ton Wattanar.

Using false for useSsl in client.connect, still expected SSL/TLS certificate, this is an unexpected behavior, how can I use non-SSL???
`An error occurred while attempting to establish an SSL or TLS connection.

The SSL certificate presented by the server is not trusted by the system for one or more of the following reasons:

1. The server is using a self-signed certificate which cannot be verified.
2. The local system is missing a Root or Intermediate certificate needed to verify the server's certificate.
3. The certificate presented by the server is expired or invalid.`

@vmakwana you can use non-SSL by set only host parameter like this client.Connect("sc.mail.com");

Update 2019 !! :)