Re: [ietf-smtp] SMTP Reply code 1yz Positive Preliminary reply

Hector Santos <> Fri, 06 March 2020 02:31 UTC

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Date: Thu, 05 Mar 2020 21:31:11 -0500
From: Hector Santos <>
Organization: Santronics Software, Inc.
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To: John C Klensin <>
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Subject: Re: [ietf-smtp] SMTP Reply code 1yz Positive Preliminary reply
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John K,

I don't think it matters because SMTP design docs do not talk about 
client/server "Keep Alive" concepts.

We could of corrected the semantics of mixed reply codes without 
removing (without explanation) 1yz reply codes.  Modern RFC5321 
clients should not have a problem.  I think the original RFC2821 4.2.1 
last paragraph applies more correctly than the current RFC5321 
paragraph replacement which asserts persistent multi-line reply codes.

I don't know what the answer is but if RFC821 legacy compliancy is 
still important, then please allow for IP literals to remain a part of 
the basic protocol.  Engineering Consistency is all implementers can 
ask for.


On 3/5/2020 3:05 PM, John C Klensin wrote:
> Hector,
> I have added a placeholder for this to the list in Appendix G
> Section 7 of the working draft.
> FWKW, my personal opinion is that would be a significant change,
> outside the scope contemplated for 5321bis.  YMMD and that is,
> IMO, a decision that can be made only by the WG when there is
> one.  However, if others agree with me, your best course forward
> is to write and post an I-D explaining what you think would be
> desirable and why, see if you can get it standardized and
> implementation reports generated, and then propose it for
> inclusion in 5321bis.
> best,
>     john
> --On Thursday, March 5, 2020 12:56 -0500 Hector Santos
> <> wrote:
>> On 3/5/2020 11:28 AM, Hector Santos wrote:
>>> I used the reply group:
>>>      1yz   Positive Preliminary reply
>> I had forgotten that RFC5321 had removed this 1yz code.
>> All because of the 1yz potentially used as a "preliminary"
>> multiple lines "1yz-" response before the final response was
>> issued and a possible legacy 821 client that looked only at
>> the first response line because it didn't expect multiple
>> lines.
>> I don't fully recall the discussions. While I would had
>> accepted the decision for backward compatibility reasons over
>> a decade ago, I am pretty sure I would of been somewhat
>> disappointed by the removal of "1yz Positive preliminary
>> reply" codes, removing even the possibility of a keep alive
>> concept.  Today speeds allow for fast data processing, so even
>> today, 5, certainly 10 minutes of idle timeout is outdated and
>> probably should be a design taboo today.  If we don't want
>> ESMTP 2821 clients to use 1yz, well, maybe for RFC5321bis, we
>> can lower the timeouts. I already do for after a successful
>> transactions where there is additional 5 minutes wait for a
>> new transaction.  I reduced to less than 1 minute to because
>> clients from the BIG boys were 99.9% of the time holding up my
>> servers and never doing a 2nd MAIL transaction.  So wcSMTP
>> will drop clients who chews up available mail service time
>> from the server threads.
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