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Re: [ietf-smtp] SMTP status codes 251 and 551

2020-02-11 04:24:51

Am 11.02.20 um 10:52 Uhr schrieb Alessandro Vesely:
On Tue 11/Feb/2020 03:45:58 +0100 John Levine wrote:
In article 
George Schlossnagle  <george(_at_)sparkpost(_dot_)com> wrote:
We see a good bit of email here and the number of 551s that seem to
indicate forwarding is being suggested is incredibly tiny.  I could run
some stats if you like, but call it < 0.0002% over the past year's bounces.
Thanks.  Do you see any 251 at all?

251's cannot be seen, except in the mail log.  While "551 send to <x>" is
manually actionable by the author who receives the bounce, 251 is not, unless
someone enables positive delivery notification.

FWIW, in my tiny log files I found a few improper replies like the following,
in the period September-December 2014:

    551 5.0.0 This message was classified as spam

and no 251 at all.

Using Courier-MTA, I'd have to devise a new add-on in order to issue these
responses using configured forward addresses.  Do Sendmail or Postfix provide
for email address portability?

I only found this reference in the release notes for sendmail 8.8.8:

        Drop recipient address from 251 and 551 SMTP responses per RFC 821.
                Problem noted by Kari E. Hurtta of the Finnish Meteorological

That doesn't sound like sendmail actually handles the forwarding.
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