On 1/14/19 8:29 PM, John Levine wrote:
When the ABNF about extended-domain was written with the comment about info derived from the TCP connection, the TCP connection was synonymous with the transport.
I don't accept that at face value.IANA has UUCP defined as a VIA link type. I highly doubt that it was added /after/ the TCP in 5321 (which you state is functionally a copy of 2821). Or even if it was posthumously added, I would expect there to be a reference to an RFC for it. Seeing as how there isn't a reference, I'm going to believe that UUCP link types were around /before the TCP link type was defined in 5321 ~> 2821. As such, I'm going to assert that UUCP link types were around (and still in use) when the ABNF about extended-domain was written. As such, I don't agree that TCP connections were synonymous with the transport.
Now the transport is TCP plus STARTTLS in various versions plus SNI,
I don't agree. SMTP transport may be predominantly TCP (UUCP is still out there, as are some other more esoteric things).
Very simply the fact that we have on going efforts to add / require STARTTLS (MTA-STS and DANE-TLS come to mind) or bare TLS (SMTPS in one form or another) tells me that the current defacto transport does not /include/ STARTTLS.
none of which was contemplated back in 2001.
I find that highly suspect. I think that someone working on SMTP in 2001 would have had some knowledge of ongoing STARTTLS work. I'll concede that it was not enough or stable enough knowledge to influence 2821.
I think it's reasonable to use extended-domain for info about the underlying transport, even if the details are not strictly about TCP.
I'm going to disagree with you. However that disagreement is more opinion and interpretation, which we obviously differ on.
After all, the rDNS name in the FROM extended-domain comes from a DNS PTR lookup of the IP address which uses IP over UDP so it's never been strictly about TCP.
The "information derived by the server from (or about) the TCP connection" is independent of how the server derives said information. It is possible that the server used TCP for DNS, or NIS(+) via TCP, or via hosts file entries. The method used to derive the information is immaterial of what the derived information is. The RFC is concerned with what the information is, NOT how it was derived.
-- Grant. . . . unix || die
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