So as usual, the online help files are abysmally vague with more yet still locked behind a paywall, and hour later I stumble on to the answer that SW doesn't provide.

Want to setup EPDM to use your email system? Do you require SSL?

If you do, EPDM does NOT support SMTP over SSL.

Finally found this thread:

that led to this Enterprise PDM Notification via GMail — CAD Dirt

Until I get archive server access, suppose I can always set up an external email account to forward back to our users that doesn't use SSL, though that seems a bit backwards.