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

On 2019-02-08 17:56:15 +0100, Dilyan Palauzov wrote:
> Hello Paul,
>
> I am suggesting to tell the sender that the message for a recipient is 
> temporary rejected, why delivering the message.
>
> Why would an mta-client change the message-id of an email having several 
> recipients on each retry?
>
> Consider this example, I wrote to a friend an email stating “Tomorrow is my 
> last day in this neighbourhood, I would enjoy meeting you once again before 
> my departure”.  This email had empty Subject: and two weeks later the 
> recipient told me, that she read only now the email, because it was delivered 
> in the Spam folder (quarantined).  In this example, the software/AI/ML 
> decided that there will be no meeting.  The real term is “false positive”.
>
> To avoid side effects of false positives, somebody has to be involved in 
> manually dealing with them.  You have to involve the recipient, the sender or 
> special staff.
>
> Obliging the recipient to deal with false positives, leads to a cancelled 
> meeting in the example here and it “is nobody’s fault”.  Besides, when the 
> recipient address is an alias for a mailbox on another provider, there is no 
> way the aliasing server can communicate to the recipient the suspicious state.
>
> Having special staff to deal with false positives is not an option in my case.
>
> So the senders must be concerned with false positives, by hard
> rejecting the email,
I agree with this (Although bounce messages are in practice hard to
understand by normal users and therefore often ignored).


> what I proposed.
But I don't think this is what you proposed. 

As I understood it, you proposed delivering a message while returning a
4xx reply to the sender. 

So the recpipient gets the message, but the sender might get a "your
message couldn't be delivered for 4 hours" notification even though it
was actually delivered. 

I think this would be very confusing.

It also doesn't help with reducing the number of delivery rounds since
the message Id isn't available at the time RCPT is received.

        hp


-- 
   _  | Peter J. Holzer    | we build much bigger, better disasters now
|_|_) |                    | because we have much more sophisticated
| |   | hjp(_at_)hjp(_dot_)at         | management tools.
__/   | http://www.hjp.at/ | -- Ross Anderson <https://www.edge.org/>

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