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

Hector Santos <hsantos@isdg.net> Thu, 05 March 2020 17:56 UTC

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Date: Thu, 05 Mar 2020 12:56:01 -0500
From: Hector Santos <hsantos@isdg.net>
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Subject: [ietf-smtp] SMTP Reply code 1yz Positive Preliminary reply
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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.

https://tools.ietf.org/html/rfc5321#section-4.2.1

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so even today, 5, certainly 10 minutes of idle timeout is outdated and 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.


-- 
HLS