Re: We need an IETF BCP for GREY LISTING
2011-10-11 19:45:50
+1
Actually, both sides benefits - The client now can better schedule its
queued attempts for accepted sessions and not wasting multiple
attempts on GL servers with *increasingly* unexpected, and IMV,
unreasonable longer delays and the GL server will see less wasted
connected sessions they will be blocking anyway, thus increasing their
availability for better mail acceptability.
If a BCP is widely supported, we should see it contribute to lower DNS
and SMTP wasted overhead.
In addition, it will MAY reduce the growing consideration to revisit
queuing strategies to consider the more complex Queue-By-MX/IP and not
just Queue-By-Email-Domain, which is part of the ordeal we are going
through with the much higher transaction results seen with GL servers.
Consider, for a bulk mail trade-based newsletter business, many of the
target email domains with different domains are being served by a
remote MX service. So for example, if among the large mailing list
there are 100 email different domains but they all hosted by a single
company, once they begin implementing GL, all those queued by domains
attempts will fail the first time.
And that all fine and the system has worked, until there is some
unexpected delay algorithm being used and your wasted attempts:
2nd attempt 5 mins later
3rd attempt 15 mins later
4rd attempt 30 mins later
5rd attempt 60 mins later
and perhaps as in some cases, much later even as long as a day later,
are all wasted attempts before it is finally accepted.
To add to this, even if if the client is using a connection sharing
feature, perhaps limiting four transactions per session, you have 25
groups that are greylisted. Less pain, but still a pain.
If there was some structure GL response, such as (suggestion only):
4xx [extended-code] GREYLIST=V1 [ID=sess-id] RETRY=retry-time
where
extended-code optional extended code for RFC2034 compliant
servers
GREYLIST=V1 BCP anchor for the structure format
ID=sess-id optional unique session-id the client can use
RETRY=retry-time server suggested time factor to reschedule
where
sess-id is opaque with no defined format, but maybe a
limited in size.
retry-time format can be of two forms:
yyyymmdd.hhmmss GMT time stamp to try again
hhmmss blocking time
But either form is fine since its:
yyymmdd.hhmmss = current datetime + hhmmss
I just indicated the RETRY=hhmmss format because GL setups already
have a "blocking time before acceptance" field concept as part of
their setup.
--
HLS
Keith Moore wrote:
I think the only real value in this extension would be to reward
clients that recognize it, by providing their users with more
predictable service (=less delay, more uniform delay).
Keith
On Oct 11, 2011, at 2:16 PM, Murray S. Kucherawy wrote:
RFC3339 instead of ISO8601, perhaps?
Of course, abusers will only pay attention to this if it benefits them and it�s cheap to do so. But they won�t be distinguishable from legitimate clients that just don�t know about this extension and retry by their own schedules, so one can�t penalize such clients for not respecting the request. On the other hand, you might be able to identify �good� clients (for some value thereof) by observing which ones do respect the request.
From: owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org [mailto:owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org] On Behalf Of Keith Moore
Sent: Tuesday, October 11, 2011 11:06 AM
To: Steve Atkins
Cc: SMTP Interest Group
Subject: Re: We need an IETF BCP for GREY LISTING
On Oct 11, 2011, at 1:45 PM, Steve Atkins wrote:
In that case, some minor extension to allow the SMTP server to communicate something a
bit more nuanced than "Go away, come back later." might have some value.
I could see value in that. I could imagine an SMTP extension which, if included, indicated that the server might send a response of the form
4xx please retry between <date-time>-<date-time>
...in response to say the MAIL (or maybe DATA) command, where <date-time> could be an ISO8601 date-time (the horror!) based on GMT (Z) and with no punctuation. If the client included a SIZE the server could even do bandwidth reservation. Of course there would be no guarantee that the second attempt wouldn't result in some sort of 4xx response for other reasons.
Greylisting servers could certainly make use of it, though I don't know if it would be a good idea to recommend that greylisting servers use it.
Keith
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- Re: We need an IETF BCP for GREY LISTING, (continued)
- RE: We need an IETF BCP for GREY LISTING, Murray S. Kucherawy
- Re: We need an IETF BCP for GREY LISTING, Steve Atkins
- Re: We need an IETF BCP for GREY LISTING, Keith Moore
- RE: We need an IETF BCP for GREY LISTING, Murray S. Kucherawy
- Re: We need an IETF BCP for GREY LISTING, Keith Moore
- Re: We need an IETF BCP for GREY LISTING,
Hector <=
- Re: We need an IETF BCP for GREY LISTING, Paul Smith
- Re: We need an IETF BCP for GREY LISTING, Hector
- RE: We need an IETF BCP for GREY LISTING, Murray S. Kucherawy
- Re: We need an IETF BCP for GREY LISTING, Dave CROCKER
- Re: We need an IETF BCP for GREY LISTING, Steve Atkins
- Re: We need an IETF BCP for GREY LISTING, Dave CROCKER
- Re: We need an IETF BCP for GREY LISTING, Richard Kulawiec
- Re: We need an IETF BCP for GREY LISTING, John Levine
- Greylisting retry hints, Hector
- Re: We need an IETF BCP for GREY LISTING, John Levine
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