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Re: [ietf-smtp] SMTP Greylisting Retry Hints + PRDR

2019-02-07 01:20:27
Hello Valdis,

On Wed, 2019-02-06 at 19:36 -0500, valdis(_dot_)kletnieks(_at_)vt(_dot_)edu 
On Wed, 06 Feb 2019 21:47:58 +0000,   said:

In any case, your draft shall state, if not included already, is that on

421|451  retry=00:00:00

after RCPT TO: the client is supposed really soon to send another MAIL 
followed by that RCPT.

After 4 decades of seeing programmers do unexpected things with sloppy specs, 
have to ask.. :)

Is the retry permitted to happen *later in the same connection*? And if so, 
is a
new EHLO or RSET required before doing so?

(and yes I'm sure that the same spamware that doesn't wait for the 220 before
sending an EHLO will retry in the same connection given half a chance...)

The purpose I am talking about is adding possibility for the same mail message 
with several recipienst, to accept the
message for some recipients and reject it for others.

In the above example, it does not really matter, if retry=00:00:00 or 
retry=00:00:02 is written.

Retrying the same RCPT TO: before doing DATA/MAIL FROM: will lead to the same 
421/451 reply.  This might be different
for grey listing.

Doing RCPT TO: after EHLO/RSET/another MAIL TO will lead to different results 
(accepting after RCPT).

I do not propose in general to change SMTP anyhow.  retry=… is a hint that can 
accelerate the delivery.


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