Re: [apps-discuss] draft-santos-smtpgrey-02: SMTP Service Extension for Greylisting Operations

[Hector Santos <[e-mail]>]

On 2/2/2014 8:14 PM, Murray S. Kucherawy wrote:
> On Sat, Feb 1, 2014 at 10:39 AM, Hector Santos <[e-mail]
> <mailto:[e-mail]>> wrote:
>
>     For our own implementation and deployments of WCSMTP.
>
>     No collections from other packages was made from a client standpoint.
>
>
> Does anyone else have current or planned implementations of this draft
> they'd like to discuss?

I have also wondered if the servers (see below) that do expose time 
hints have package companion clients that support it.

>
>     Many Greylisting servers do issue a time hint in their 45x
>     greylisting responses in various forms. � We can only speculate if
>     other clients are parsing this non-standard information and
>     leveraging it for their outbound mail retry scheduling logic. �Our
>     client parses for the common format seen out there, including the
>     proposed format.
>
>
> Can you point to some of the server implementations that do this?� Are
> they following the syntax in this draft?

I can't tell you of brands, but section 2.4, summaries the ones I have 
collected in the wild (from our outbound logs) that issue retry time 
hints in their temporary reject responses.

   http://tools.ietf.org/html/draft-santos-smtpgrey-02#section-2.4

   421 This server implements greylisting, please try again in # seconds
   450 4.7.1 <RCPT>: Recipient address rejected: Greylisted for # minutes
   450 4.7.1 <RCPT>: Recipient address rejected: Greylisted for # seconds
   451 4.7.1 Greylisting in action, please come back in HH:MM:SS
   451 Greylisted for # seconds

So the intent is there by greylisting servers to provide "information" 
for future clients to use when possible.

In practice, I have found the servers do honor and are correct with 
the times.  I have not found any instance of the info being wrong.  If 
it said wait X mins, your client waited X mins and there was no more 
delivery blocks/delays. If I have found any instance where it was just 
wrong, then I wouldn't had bother with this.

Thanks

-- 
HLS