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Re: What does Postfix do with a 554 on connection?

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  • Wietse Venema
    ... As of RFC 2821, The SMTP protocol allows a server to formally reject a transaction while still allowing the initial connection as follows: a 554 response
    Message 1 of 6 , Mar 19, 2013
      Reindl Harald:
      > Am 20.03.2013 00:54, schrieb Wietse Venema:
      > > Reindl Harald:
      > >>> I don't think that Postfix has ever distinguished between 5xx codes
      > >>> at this protocol stage. The documentation says:
      > >>>
      > >>> smtp_skip_5xx_greeting (default: yes)
      > >>>
      > >>> Skip remote SMTP servers that greet with a 5XX status code
      > >>> (go away, do not try again later).
      > >>>
      > >>> By default, the Postfix SMTP client moves on the next mail
      > >>> exchanger. Specify "smtp_skip_5xx_greeting = no" if Postfix
      > >>> should bounce the mail immediately. The default setting is
      > >>> incorrect, but it is what a lot of people expect to happen
      > >>
      > >> now i am more confused as before
      > >>
      > >> what the documentation above and the description says is not to
      > >> bounce it, the RFC seems to indicate this too, so i do not get
      > >> "The default setting is incorrect" in my picture
      > >
      > > As I wrote, I will update the documentation which predates the
      > > time that 554 was a defined greeting code
      >
      > sorry if i sound stupid this time
      >
      > should it be bounced and unsubscribed or left in the newsletter-list?
      > from a users point of view "greeting code" is vague

      As of RFC 2821,

      The SMTP protocol allows a server to formally reject a transaction
      while still allowing the initial connection as follows: a 554
      response MAY be given in the initial connection opening message
      instead of the 220. A server taking this approach MUST still wait
      for the client to send a QUIT (see section 4.1.1.10) before closing
      the connection and SHOULD respond to any intervening commands with
      "503 bad sequence of commands". Since an attempt to make an SMTP
      connection to such a system is probably in error, a server returning
      a 554 response on connection opening SHOULD provide enough
      information in the reply text to facilitate debugging of the sending
      system.

      My plan is to remove smtp_skip_5xx_greeting because for the past
      10+ years it is no longer a valid response to bounce mail.

      Now, it is possible that some SMTP client implementations treat it
      as a bounce response, but those clients are out of spec.

      Wietse
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