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240658Re: backupmx with Postfix

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  • Nicolas Letellier
    Jul 1 10:21 AM
      On Tue, 01 Jul 2008 17:33:09 +0200
      mouss <mouss@...> wrote:

      > Nicolas Letellier wrote:
      > > On Tue, 01 Jul 2008 11:04:53 +0200
      > > mouss <mouss@...> wrote:
      > >
      > >> If you have relay_recipient_maps set, then postfix will _reject_, not
      > >> bounce. it is the "previous" MTA that generates the bounce. This is why
      > >> you should reject on the first server that you manage and let others
      > >> bounce or do whatever they want.
      > >>
      > > But, if Postfix rejects a mail, it sends a mail to inform that the mail has been rejected or not?
      > > If rejecting a mail, Postfix send it to /dev/null and do not send any mails to sender, it's a good news!
      > >
      > >
      > >
      > do not confuse "reject" and "bounce".
      > here is a reject example: C is a remote client (MTA or other). S is your
      > server.
      > C->S: connect
      > S->C: show greeting banner
      > C->S: says helo
      > S->C: show supported extensions (auth, tls, ... etc)
      > C->S: MAIL FROM: <sender@...>
      > S->C: OK
      > C->S: RCPT TO: <invalid@...>
      > S->C: rejected. recipient does not exist
      > C->S: QUIT
      > no message is exchanged here. your server does nothing after this. it
      > does not send a bounce. If C is a normal MTA, it is its responsibility
      > to generate a bounce, but this none of our business: we don't care.
      > If on the other hand your server is misconfigured, it will accept the
      > mail during the smtp transaction. then later it will find out that it
      > cannot deliver the message. it will then generate a bounce and send it
      > to the original sender. sometime ago, this was ok, but since a lot of
      > spam uses forged addresses, such bounces go to innocent people who did
      > not send anything. This is backscatter.
      Ok, thanks for the explication! This will help me.

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