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

2020-02-11 03:52:40
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?


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