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smtp_fallback_relay and greylists

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  • Rafael Azevedo - IAGENTE
    Hello guys! I was reading the smtp_fallback_relay doc at http://www.postfix.org/postconf.5.html#smtp_fallback_relay and couldn t be able to make it work. It
    Message 1 of 12 , Jan 16, 2013
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      Hello guys!

      I was reading the smtp_fallback_relay doc at http://www.postfix.org/postconf.5.html#smtp_fallback_relay and couldn't be able to make it work.

      It says:
      smtp_fallback_relay (default: $fallback_relay)
      […]

      With bulk email deliveries, it can be beneficial to run the fallback relay MTA on the same host, so that it can reuse the sender IP address. This speeds up deliveries that are delayed by IP-based reputation systems (greylist, etc.).

      The fallback relays must be SMTP destinations. Specify a domain, host, host:port, [host]:port, [address] or [address]:port; the form [host] turns off MX lookups. If you specify multiple SMTP destinations, Postfix will try them in the specified order.


      So I had on my main.cf this of host-x.domain server:
      smtp_fallback_relay = host-x.domain

      And the logs just shows this:
      postfix/error[18333]: 84F911A02BC58: to=<user@...>, relay=none, delay=1143, delays=0/1143/0/0, dsn=4.3.5, status=deferred (delivery temporarily suspended: mail for host-x.domain loops back to myself)

      Any idea of what I'm doing wrong?

      Thanks in advance.
      -- Rafael
    • Wietse Venema
      ... It says use the same host. It does not say use the same myhostname setting. Wietse
      Message 2 of 12 , Jan 16, 2013
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        Rafael Azevedo - IAGENTE:
        > With bulk email deliveries, it can be beneficial to run the fallback
        > relay MTA on the same host, so that it can reuse the sender IP
        > address. This speeds up deliveries that are delayed by IP-based
        > reputation systems (greylist, etc.).
        ...
        > And the logs just shows this: postfix/error[18333]: 84F911A02BC58:
        > to=<user@...>, relay=none, delay=1143, delays=0/1143/0/0,
        > dsn=4.3.5, status=deferred (delivery temporarily suspended: mail
        > for host-x.domain loops back to myself)

        It says use the same host. It does not say use the same
        myhostname setting.

        Wietse
      • Rafael Azevedo
        ... Thanks once again Wietse! Your help is very appreciated. I ll try to work on this. BR, - Rafael
        Message 3 of 12 , Jan 17, 2013
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          > It says use the same host. It does not say use the same
          > myhostname setting.

          Thanks once again Wietse! Your help is very appreciated.

          I'll try to work on this.

          BR,
          - Rafael
        • Rafael Azevedo
          ... Wietse, Could you please tell me the difference of same host and myhostname ? What I understood from the document is that its suggested to use the same
          Message 4 of 12 , Jan 17, 2013
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            > It says use the same host. It does not say use the same
            > myhostname setting.

            Wietse,

            Could you please tell me the difference of "same host" and "myhostname"?

            What I understood from the document is that its suggested to use the same host/ip to re-send the message in cases of greylists. In my case, each postfix server uses myhostname to determinate the server's host (each host has its own ip).

            So I imagined that I should use the same myhostname in smtp_fallback_relay in order to have it retrying to send the messages that were deferred because of graylists.

            Would you please give me a light on this?

            Thanks in advance.
            - Rafael
          • Stan Hoeppner
            ... A host is a computer (or virtual machine). myhostname is a Postfix parameter. Now plug these into the context of Wietse s statement to you and you should
            Message 5 of 12 , Jan 17, 2013
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              On 1/17/2013 5:16 AM, Rafael Azevedo wrote:

              > Could you please tell me the difference of "same host" and "myhostname"?

              A host is a computer (or virtual machine). myhostname is a Postfix
              parameter. Now plug these into the context of Wietse's statement to you
              and you should understand.

              --
              Stan
            • Rafael Azevedo
              ... Thanks Stan! But if I point it to another host (different than myhostname) it will send through another IP right? I m not sure how can I get through
              Message 6 of 12 , Jan 17, 2013
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                > A host is a computer (or virtual machine). myhostname is a Postfix
                > parameter. Now plug these into the context of Wietse's statement to you
                > and you should understand.

                Thanks Stan!

                But if I point it to another host (different than myhostname) it will send through another IP right? I'm not sure how can I get through greylist this way.

                This concept is still not clear for me.

                - Rafael
              • Wietse Venema
                ... host = computer (operating system on top of real or virtual hardware) MTA = postfix The text in main.cf assumes that both non-fallback and fallback MTA run
                Message 7 of 12 , Jan 17, 2013
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                  Rafael Azevedo:
                  > > A host is a computer (or virtual machine). myhostname is a Postfix
                  > > parameter. Now plug these into the context of Wietse's statement to you
                  > > and you should understand.
                  >
                  > Thanks Stan!
                  >
                  > But if I point it to another host (different than myhostname) it
                  > will send through another IP right? I'm not sure how can I get
                  > through greylist this way.

                  host = computer (operating system on top of real or virtual hardware)
                  MTA = postfix

                  The text in main.cf assumes that both non-fallback and fallback
                  MTA run on the same host and that they send mail from the same
                  source IP address. You could for example:

                  - Configure both MTAs to use the same smtp_bind_address.

                  - Configure each MTA with its own IP address and play with NAT.

                  Wietse
                • Steve Jenkins
                  ... Could this be achieved with a single instance of Postfix on one host machine configured for 2+ virtual domains with the same domain name (
                  Message 8 of 12 , Jan 17, 2013
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                    On Thu, Jan 17, 2013 at 5:28 AM, Wietse Venema <wietse@...> wrote:
                    host = computer (operating system on top of real or virtual hardware)
                    MTA = postfix

                    The text in main.cf assumes that both non-fallback and fallback
                    MTA run on the same host and that they send mail from the same
                    source IP address. You could for example:

                    - Configure both MTAs to use the same smtp_bind_address.

                    - Configure each MTA with its own IP address and play with NAT.

                    Could this be achieved with a single instance of Postfix on one host machine configured for 2+ virtual domains with the same domain name (mailer1.example.com, mailer2.example.com, etc.), or would it need to be two separate instances of Postfix running on the same host?

                    Regardless, if they two MTAs used the same smtp_bind_address, wouldn't that mean that only one of them would match the host's reverse DNS lookup, and that the other would have mail rejected by remote hosts that verify the reverse IP matches the sending IP?
                  • Wietse Venema
                    ... The idea of smtp_fallback_relay is to NOT share the mail queue. ... smtp_bind_address sets the SOURCE IP address. Wietse
                    Message 9 of 12 , Jan 17, 2013
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                      Steve Jenkins:
                      > Could this be achieved with a single instance of Postfix on one
                      > host machine configured for 2+ virtual domains with the same domain
                      > name ( mailer1.example.com, mailer2.example.com, etc.), or would
                      > it need to be two separate instances of Postfix running on the
                      > same host?

                      The idea of smtp_fallback_relay is to NOT share the mail queue.

                      > Regardless, if they two MTAs used the same smtp_bind_address,
                      > wouldn't that mean that only one of them would match the host's
                      > reverse DNS lookup, and that the other would have mail rejected
                      > by remote hosts that verify the reverse IP matches the sending IP?

                      smtp_bind_address sets the SOURCE IP address.

                      Wietse
                    • Rafael Azevedo
                      ... Yes, but I cant have 2 servers with same smtp_bind_address - Rafael
                      Message 10 of 12 , Jan 17, 2013
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                        > smtp_bind_address sets the SOURCE IP address.

                        Yes, but I cant have 2 servers with same smtp_bind_address

                        - Rafael
                      • Wietse Venema
                        ... Yes, you can, as long as the MTAs run on the SAME HOST. Wietse
                        Message 11 of 12 , Jan 17, 2013
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                          Rafael Azevedo:
                          > > smtp_bind_address sets the SOURCE IP address.
                          >
                          > Yes, but I cant have 2 servers with same smtp_bind_address

                          Yes, you can, as long as the MTAs run on the SAME HOST.

                          Wietse
                        • Wietse Venema
                          ... Definitely not. Wietse
                          Message 12 of 12 , Jan 17, 2013
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                            Rafael Azevedo:
                            > > Yes, you can, as long as the MTAs run on the SAME HOST.
                            >
                            > Hmm.. Is there anyway we can have multiple postfix instances sharing
                            > the same queue?

                            Definitely not.

                            Wietse
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