On 06/10/2019 09:04, Viruthagiri Thirumavalavan wrote:
SMTP has port 465 for Implicit TLS. Port 465 was discontinued in the late
90’s in favour of STARTTLS extension. Two decades later that port got
reassigned to "Message Submission" in 2018.
So the “submission” part supports Implicit TLS. But “Transfer” mode is
still missing the “Implicit TLS”. We can't use the same port 465 for
"Transfer" mode since all ISPs wanna block only direct-to-mx connections to
prevent outgoing spam and not the message submission connections. So there
will be a conflict if we use port 465 for both "submission" and "transfer".
That's why I proposed a new port 26.
An alternative might be to use TCP ENO (RFC 8547) and tcpcrypt
(RFC 8548), sitting on port 25 ?
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