BB
https://www.mailgun.com/blog/which-smtp-port-understanding-ports-25-465-587/
Port 465:
IANA has reassigned a new service to this port, and it should no longer be used for SMTP communications.
However, because it was once recognized by IANA as valid, there may be legacy systems that are only capable of using this connection method. Typically, you will use this port only if your application demands it. A quick Google search, and you'll find many consumer Inbox Service Providers' (ISPs) articles that suggest port 465 as the recommended setup. However, we do not recommend it, as it is not RFC compliant.