Symptoms

SmartForm email event throwing the error: "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 SMTP Client was not authenticated to send anonymous mail during MAIL FROM"
 

Diagnoses

This looks to be a known issue affecting SmartForms email events.
 

Resolution

Work around by creating a simple workflow that just sends an email and fire it off via a SmartForm rule. One can set it up to pass in addresses from the form as well.