SmtpClient wont authenticate over SSL/TLS (not pointing to gmail)

Question

I have an ssl/tls server (nodejs) that acts as a proxy to postfix/sendmail to perform some pre-processing/data aquisition on outgoing mail.

From C#, I can manually

Answer 1

Solved a while back, forgot to post the answer.

The .NET smtp client, along with most smtp client libraries, does not support initiating communications via ssl/tls. It requires that the smtp server support initiating communications unencrypted, and then transitioning to an encrypted connection using the "upgrade" command (this is almost always handled behind the scenes by the SMTP client library).

At the time, I was connecting to a semi-custom smtp server that was proxying postfix, and this custom solution only supported connecting initially via ssl/tls. Have since started using Haraka for my SMTP server, which supports all SMTP standards as well as providing me with the plugin capability I needed.