You got to configure the WF MAiler outbount with the mail server's hostname, port and you should provide user and pass if you don't have relay access to the mail server..
Check with your MAil server admin and ensure what needs to be configured for both.
Do we need to communicate with the SMTP mailer server using SSL/TLS?
Do we need to communicate with the IMAP mailer server using SSL/TLS?
According to the answers, configure your WF mailer?
If for instance you need to speak SSL/TLS with the SMTP MAiler Serve, then you need to configure outbound SSL for the WF Mailer.. I think you got it.
startttls is not a protocol. It is a like command.
Yours should be ssl/tls. Speak with your mail server admin and learn the protocol, get the certificates and implement SSL conf on WF Mailer.