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

2019-02-09 13:11:38
On Sat, 09 Feb 2019 12:53:09 +0000, Ð?илÑ?н Ð?алаÑ?зов said:

I propose inserting in the draft under section â??3.  SMTP Service Keywordâ?? 
the text:

When the service keyword 250-GREYLIST is announced, it indicates that the
client SHALL keep the IP address on retries.

So riddle me this:  What then happens to an e-mail if it's next attempt is from
a different IP address?  (Quite possible if the outbound client is a cluster of
machines with a shared mail queue, or an HA pair that's fallen over to the other
IP address, or....)  Perhaps this only merits a SHOULD rather than a SHALL?

â??If a SMTP client is rejected by the Greylisting Server during the
  session, the client SHOULD NOT attempt to start a new transaction
 during the same session and SHOULD immediately issue a QUIT command
  to end the session. â??

I do not like this text, as it is against the idea of accepting one/few RCPT
per transaction, and telling all the other recipients â??421 â?¦ retry=0â??.

Agreed on that - it means that if there are multiple mail items queued for
a delivery to a host that has been unreachable for some amount of time,
the client can't complete running the queue - even if the remaining messages
would not have been greylisted.

And if you were planning to greylist all the remaining messages, why aren't
we using a simple '250-GREYLIST retry=00:10:00' in the EHLO response?

The PRDR-after-DATA proposal will make progress, if providers are willing to
switch the work on dealing with spam folders to the sender.  As user I want 
to deal with Spam folder, and this switch makes it possible.

And as a user, if the sender is doing the spam management, you *can't* deal
with your spam folder anymore.  Which will totally suck if the sender decides 
since the mail got greylisted, it must be spam - and it's a false positive on
an actually important mail like a bank notification.  Remember - spam folders
exist precisely because spam detection isn't perfect.

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