[mike-cardwell]

Port 465 is for mail submission. It's there for authenticated communication between clients and servers. It has never been used for communication from server to server and was never intended to be. Port 587 has the same purpose (mail submission), but has a plain text protocol specific negotiation at the beginning which matches that for server to server mail transfer on port 25.

[lvh]

True, but the underlying question is still interesting: why isn't there a similar TLS-only port for MTA-MTA and we all agree to try to connect there first

[flashmob]

Oops, I see, was assuming it was used for MTA too! So there was never really a dedicated TLS port for MTA to begin with?