Hello Vince, assuming you've already confirmed you have an SMTP port 25 instance set up with TLS enabled, I believe you can correct this by navigating to Settings>Protocols>SMTP Out and enable the toggle for Enable TLS if supported by the remote server. Please let me know if that works for you.
Kyle Kerst
System/Network Administrator
SmarterTools Inc.
(877) 357-6278
www.smartertools.com