I’m curious about the reason behind this change:
Sending mail is now possible on port 465 with the “SSL” or “TLS” option in mail clients, and this is now the recommended setting. Port 587 with STARTTLS remains available but should be avoided when configuring new mail clients.
From what I read, 587 should be the default:
IANA has reassigned a new service to this port, and it should no longer be used for SMTP communications.
This is the default mail submission port. When an email client or outgoing server is submitting an email to be routed by a proper mail server, it should always use SMTP port 587 as the default port.
So why we went back to 465?