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Re: Re: Routing Control of locally generated bounces in Postfix

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  • nullnullachtfuenfzehn@...
    ... My apologies, I try to be more detailed. 2 organisations in 2 private networks. 2 private DNS setups in both organisations, completely independant from
    Message 1 of 7 , Apr 19 3:28 AM
      > Your description is too sketchy. Please choose appropriate domain
      > names under example.com, example.net, example.org, ... (if the real
      > domain names are sensitive) that make it clear what sender and
      > recipient addresses look like in each direction.
      >
      > You should be able to the right thing with transport_maps, but specific
      > guidane requires a less vague description.

      My apologies, I try to be more detailed.

      2 organisations in 2 private networks.
      2 private DNS setups in both organisations, completely independant from each other.
      Mail between the 2 organisations is routed via MX lookups which point to our Postfix.

      organisation A has the following MX records in its own DNS:

      @...
      @... <- points to our postfix

      organisation B has the following MX records in its own DNS:

      @...
      @...
      @... <- points to our postfix

      The postfix host uses the DNS in organisation A and has a multi instance setup.

      The first instance routes only mail from A to B. It uses smtpd_sender_restrictions=reject_unknown_sender_domain and relays all mail to a relayhost.
      Everything is fine with this instance.

      The second instance routes only mail from B to A. Destination lookups are done via A´s DNS.
      Everything is fine with mail from senders in @... to recipients in @....
      The problem rises with mail originating from senders in @... to recipients in @....
      Because the destination server in A also does a smtpd_sender_restrictions=reject_unknown_sender_domain and @... is unknown in A´s DNS the sender address is rejected.
      The missing MX Record in A´s DNS is ok, because senders in @... are not supposed to participate mail exchange with @... and vice versa.
      But where to deliver the bounce?
      The postfix host uses A´s DNS and the transport_maps are not complete due to not allowed zone transfers from some DNS servers in B.
      I tried sender_dependent_relayhost_maps but because it only works on the envelope sender, locally and remotely bounces are treated equally.

      My end-goal if possible is: distinguish between remotely and locally generated bounces and send locally generated bounces to a relayhost which can deliver the bounce to recipients in @....
      Can this behavior somehow be accomplished or must I go through the prcoess of log file analysis to identify the missing record @... in transport_maps?

      Peter
    • Timo Röhling
      ... Why exactly is there a bounce in the first place? If the @A1 MX rejects mail from @B2 during the SMTP session, it never receives responsibility for any
      Message 2 of 7 , Apr 19 4:39 AM
        Am 2013-04-19 12:28, schrieb nullnullachtfuenfzehn@...:
        > The problem arises with mail originating from senders in
        > @... to recipients in @....
        > Because the destination server in A also does a
        > smtpd_sender_restrictions=reject_unknown_sender_domain and
        > @... is unknown in A´s DNS the sender address is rejected.
        > The missing MX Record in A´s DNS is ok, because senders in
        > @... are not supposed to participate mail exchange with
        > @... and vice versa.
        > But where to deliver the bounce?
        Why exactly is there a bounce in the first place? If the @A1 MX rejects
        mail from @B2 during the SMTP session, it never receives responsibility
        for any bounces. Unless of course you accept the mail first and then
        decide later to bounce it. But why would you do that?

        -Timo
      • nullnullachtfuenfzehn@...
        ... Timo you opened my eyes. We have the same DNS information as the destination host has. With smtpd_sender_restrictions=reject_unknown_sender_domain
        Message 3 of 7 , Apr 19 9:06 AM
          > Am 2013-04-19 12:28, schrieb nullnullachtfuenfzehn@...:
          > > The problem arises with mail originating from senders in
          > > @... to recipients in @....
          > > Because the destination server in A also does a
          > > smtpd_sender_restrictions=reject_unknown_sender_domain and
          > > @... is unknown in A´s DNS the sender address is rejected.
          > > The missing MX Record in A´s DNS is ok, because senders in
          > > @... are not supposed to participate mail exchange with
          > > @... and vice versa.
          > > But where to deliver the bounce?
          > Why exactly is there a bounce in the first place? If the @A1 MX rejects
          > mail from @B2 during the SMTP session, it never receives responsibility
          > for any bounces. Unless of course you accept the mail first and then
          > decide later to bounce it. But why would you do that?
          >

          Timo you opened my eyes.
          We have the same DNS information as the destination host has. With smtpd_sender_restrictions=reject_unknown_sender_domain activated in this postfix instance the problem silently disappears.

          Thanks a lot
          Peter
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