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

2020-03-05 11:56:26

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 Today speeds allow for fast data processing, so even today, 5, certainly 10 minutes of idle timeout is outdated and probably should be a design taboo today.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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