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Re: [ietf-smtp] SMTP Retrying/Sending Strategy on 452 / 4.5.3

2019-02-16 08:25:17
Hello Santos,

your draft describes an existing server’s defering strategy and advices clients 
how to act, when this defering strategy
is in effect.  One of the essential parts of your draft is writing down the 
idea (formalizing) for the smtp-clients to
reuse the IP address on retrying, when grey listing is in effect.  Whether grey 
listing is in effect, does not depend on
a 250-GREYLIST or retry= information.

I suggest you include in the draft how a client can recognize that greylisting 
deferring is in effect and, based on the
outcome, decide to use or not other IP addresses for subsequent/immediate 

If retry=0 is (intentionaly) left undefined, then the draft shall state this, 
and probably suggest what clients shall do
on retry=0.  (E.g. ignore).  Keeping retry=0 this way, because anything else is 
not backward compatible with
implementations of a draft, does not necessary mean that there is a consensus.

Your draft states:
   If a SMTP server offers a "retry=time-delay" hint which results in a
   wasted 2nd attempt and requires additional attempts, the SMTP client
   MAY begin to ignore the server's "retry=time-delay" hint after the
   2nd wasted retry.  The SMTP client implementation can decide what
   limits to place on honoring "retry=time-delay" hints and wasted
   attempts it provides.

I suggested previously, and this was not tackled, that a retry is not wasted, 
if the remaining number of recipients has
decreased during the retry.


On Wed, 2019-02-13 at 15:27 -0500, John Levine wrote:
In article 
<12803(_dot_)1550087591(_at_)turing-police(_dot_)cc(_dot_)vt(_dot_)edu> you 
On Wed, 13 Feb 2019 12:22:09 +0000, Дилян Палаузов said:

Is publishing 1024 distinct IPv6 addresses for MX on a domain a good idea

Only if you're *really* sure that everybody who wants to talk to you 
at least EDNS0 and doesn't block tcp/53 :)

Let me simplify that answer:

No, it is not.


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