Port 465 is Normally the Implicit SSL SMTP Port, but not always…
If you open a DOS prompt and telnet to an SMTP server (typically port 25 for non-SSL, port 465 for SSL), you should get a human-readable printable-text “HELLO” message from the non-SSL port, but binary SSL-handshake protocol gobbly-gook from an implicit SSL port.
> telnet mail.chilkatsoft.com 25 220 mail.chilkatsoft.com ESMTP MailEnable Service, Version: 0-1.85- ready at 05/30/08 08:04:19
> telnet smtp.gmail.com 465 The response is non-printable binary data...
If however, you telnet to port 465 and get a human-readable response, then the SMTP server is not expecting an implicit SSL/TLS connection. Most likely, it’s expecting the connection to be converted to TLS via the STARTTLS command.
> telnet smtpx17.msoutlookonline.net 465 220 smtpx17.msoutlookonline.net Microsoft ESMTP MAIL Service ready at Fri, 30 May 2008 05:09:46 -0700
In terms of using Chilkat MailMan, three properties are involved: SmtpPort, SmtpSsl, StartTLS.
If the SMTP server expects an implicit SSL/TLS connection on the port, set SmtpSsl = true, and StartTLS = false.
If the SMTP server expects a non-SSL connection to be converted to a TLS connection, set SmtpSsl = false, but set StartTLS = true.
The SmtpPort, of course, should be set to the correct port value…