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duplicate email issue with list

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  • Quanah Gibson-Mount
    One of our customers has an interesting setup where they did the following: a) Created 50 users b) Added a secondary address for the 50 users to an external
    Message 1 of 6 , Sep 26, 2013
      One of our customers has an interesting setup where they did the following:

      a) Created 50 users

      b) Added a secondary address for the 50 users to an external server with 50
      users (So any email sent to user@server also gets copied to user@server2).

      c) Created a list with the 50 users as members. Lists are just a simple
      ldap member: of list.

      If an email is sent to the list:

      The 50 users on the server each get a copy

      The 50 users on the second server get two copies

      I've verified I can recreate this issue with a list of 30 users with the
      same configuration. I don't see it with a list of 25 users. I'm sure
      there's a postconf key that would control this, but I haven't had any luck
      tracking it down. Thoughts welcome. ;)

      --Quanah

      --

      Quanah Gibson-Mount
      Lead Engineer
      Zimbra Software, LLC
      --------------------
      Zimbra :: the leader in open source messaging and collaboration
    • Wietse Venema
      ... Suggestions: 1) Look at the maillog files of primary and secondary server, with particular attention to the nrcpt and orig_to fields. 2) 50 Is a magical
      Message 2 of 6 , Sep 26, 2013
        Quanah Gibson-Mount:
        > One of our customers has an interesting setup where they did the following:
        >
        > a) Created 50 users
        >
        > b) Added a secondary address for the 50 users to an external server with 50
        > users (So any email sent to user@server also gets copied to user@server2).
        >
        > c) Created a list with the 50 users as members. Lists are just a simple
        > ldap member: of list.
        >
        > If an email is sent to the list:
        >
        > The 50 users on the server each get a copy
        >
        > The 50 users on the second server get two copies
        >
        > I've verified I can recreate this issue with a list of 30 users with the
        > same configuration. I don't see it with a list of 25 users. I'm sure
        > there's a postconf key that would control this, but I haven't had any luck
        > tracking it down. Thoughts welcome. ;)

        Suggestions:

        1) Look at the maillog files of primary and secondary server, with
        particular attention to the nrcpt and orig_to fields.

        2) 50 Is a magical number; it is the default_destination_recipient_limit
        (the number of recipients per SMTP mail transaction). When a queue
        file has more than 50 SMTP recipients, these will be delivered in
        more than one mail transaction.

        3) Postfix tries to preserve the x-original-to address by default,
        meaning it will not eliminate duplicate recipients of the same
        message that differ in the x-original-to address.

        Wietse
      • Viktor Dukhovni
        ... What is doing the rewriting, and does the site employ any content filters. An ovious way to lose is to pass the message through multiple stages of
        Message 3 of 6 , Sep 26, 2013
          On Thu, Sep 26, 2013 at 01:03:26PM -0700, Quanah Gibson-Mount wrote:

          > a) Created 50 users
          >
          > b) Added a secondary address for the 50 users to an external server
          > with 50 users (So any email sent to user@server also gets copied to
          > user@server2).
          >
          > c) Created a list with the 50 users as members. Lists are just a
          > simple ldap member: of list.
          >
          > If an email is sent to the list:
          >
          > The 50 users on the server each get a copy
          >
          > The 50 users on the second server get two copies
          >
          > I've verified I can recreate this issue with a list of 30 users with
          > the same configuration. I don't see it with a list of 25 users.
          > I'm sure there's a postconf key that would control this, but I
          > haven't had any luck tracking it down. Thoughts welcome. ;)

          What is doing the rewriting, and does the site employ any content
          filters. An ovious way to "lose" is to pass the message through
          multiple stages of deliveries each which of maps:

          user -> user, forward

          envelope splitting (at ~50 users) will prevent duplicate recipient
          elimination from always eliminating the resulting duplicates.

          The right solution is to only do the rewrite in one place. Hence
          the infamous:

          http://www.postfix.org/postconf.5.html#receive_override_options

          I prefer to use multiple instances, with virtual rewriting in the
          input instance only and a content filter in between.

          --
          Viktor.
        • Stefan Foerster
          ... Does the issue persist if a owner-listname alias is created, pointing to e.g. postmaster?
          Message 4 of 6 , Sep 26, 2013
            * Quanah Gibson-Mount <quanah@...>:
            > One of our customers has an interesting setup where they did the following:
            >
            > a) Created 50 users
            >
            > b) Added a secondary address for the 50 users to an external server
            > with 50 users (So any email sent to user@server also gets copied to
            > user@server2).
            >
            > c) Created a list with the 50 users as members. Lists are just a
            > simple ldap member: of list.
            >
            > If an email is sent to the list:
            >
            > The 50 users on the server each get a copy
            >
            > The 50 users on the second server get two copies
            >
            > I've verified I can recreate this issue with a list of 30 users with
            > the same configuration. I don't see it with a list of 25 users.
            > I'm sure there's a postconf key that would control this, but I
            > haven't had any luck tracking it down. Thoughts welcome. ;)

            Does the issue persist if a owner-listname alias is created, pointing
            to e.g. postmaster?
          • Viktor Dukhovni
            ... 1. The magic 50 strongly points at SMTP delivery, not local. 2. The owner-listname alias is a feature of the local(8) delivery agent, which is almost
            Message 5 of 6 , Sep 27, 2013
              On Fri, Sep 27, 2013 at 07:17:08AM +0200, Stefan Foerster wrote:

              > > I've verified I can recreate this issue with a list of 30 users with
              > > the same configuration. I don't see it with a list of 25 users.
              > > I'm sure there's a postconf key that would control this, but I
              > > haven't had any luck tracking it down. Thoughts welcome. ;)
              >
              > Does the issue persist if a owner-listname alias is created, pointing
              > to e.g. postmaster?

              1. The magic 50 strongly points at SMTP delivery, not local.

              2. The owner-listname alias is a feature of the local(8) delivery agent,
              which is almost certainly not used in this case.

              3. The local delivery agent uses a large duplicate elimination table,
              and alias expansion is generally handled internally without a second
              transit through the queue.

              So no, that is a not a good lead.

              --
              Viktor.
            • Quanah Gibson-Mount
              --On Thursday, September 26, 2013 4:38 PM -0400 Wietse Venema ... Ok, will do. ... Definitely not this, the first thing I tried was changing this value from 50
              Message 6 of 6 , Oct 7, 2013
                --On Thursday, September 26, 2013 4:38 PM -0400 Wietse Venema
                <wietse@...> wrote:

                > Quanah Gibson-Mount:
                >> One of our customers has an interesting setup where they did the
                >> following:
                >>
                >> a) Created 50 users
                >>
                >> b) Added a secondary address for the 50 users to an external server with
                >> 50 users (So any email sent to user@server also gets copied to
                >> user@server2).
                >>
                >> c) Created a list with the 50 users as members. Lists are just a simple
                >> ldap member: of list.
                >>
                >> If an email is sent to the list:
                >>
                >> The 50 users on the server each get a copy
                >>
                >> The 50 users on the second server get two copies
                >>
                >> I've verified I can recreate this issue with a list of 30 users with the
                >> same configuration. I don't see it with a list of 25 users. I'm sure
                >> there's a postconf key that would control this, but I haven't had any
                >> luck tracking it down. Thoughts welcome. ;)
                >
                > Suggestions:
                >
                > 1) Look at the maillog files of primary and secondary server, with
                > particular attention to the nrcpt and orig_to fields.

                Ok, will do.

                > 2) 50 Is a magical number; it is the default_destination_recipient_limit
                > (the number of recipients per SMTP mail transaction). When a queue
                > file has more than 50 SMTP recipients, these will be delivered in
                > more than one mail transaction.

                Definitely not this, the first thing I tried was changing this value from
                50 to 300. ;)

                > 3) Postfix tries to preserve the x-original-to address by default,
                > meaning it will not eliminate duplicate recipients of the same
                > message that differ in the x-original-to address.

                Ok, thanks.

                --Quanah

                --

                Quanah Gibson-Mount
                Architect - Server
                Zimbra Software, LLC
                --------------------
                Zimbra :: the leader in open source messaging and collaboration
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