Problem with SMTP configuration

[djr013]

Port 465 was, many years ago, SMTP over SSL/TLS – it doesn’t use STARTTLS. I say “was”, because it’s been deprecated for so many years that the IETF has deregistered smtps as a protocol. You should use either port 25 (SMTP) or port 587 (submission) and STARTTLS.

There’s a January 2018 IETF RFC which recommends use of port 465 for “implicit” TLS. A motivation for this is the increasing trend for mandatory encryption, which renders STARTTLS somewhat redundant. RFC 8314 - Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access