ASP.NET Core + Amazon SES: The remote certificate is invalid according to the validation procedure
<p>I am trying to send email using ASP.NET Core, MailKit and Amazon SES:</p>

<pre><code>  using (SmtpClient client = new SmtpClient(new ProtocolLogger("smtp.log"))) {
      client.Connect("email-smtp.us-east-1.amazonaws.com", 587, SecureSocketOptions.StartTls);
      client.Authenticate("myusername", "mypassword");
      await client.SendAsync(message);
      client.Disconnect(true);
  }
</code></pre>

<p>I keep getting the error "The remote certificate is invalid according to the validation procedure.".</p>

<p>And the log file shows:</p>

<pre><code>Connected to smtp://email-smtp.us-east-1.amazonaws.com:587/?starttls=always
S: 220 email-smtp.amazonaws.com ESMTP SimpleEmailService-1737464811 qt5bXhIgVseJaHPspjp4
C: EHLO [127.0.0.1]
S: 250-email-smtp.amazonaws.com
S: 250-8BITMIME
S: 250-SIZE 10485760
S: 250-STARTTLS
S: 250-AUTH PLAIN LOGIN
S: 250 Ok
C: STARTTLS
S: 220 Ready to start TLS
</code></pre>

<p>What am I missing?</p>