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Re: Separate Submission Instance on Same IP as MX

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  • Wietse Venema
    ... If you use different MTAs, then use different myhostname AND different inet_interfaces settings. Otherwise it is just too easy to screw up and have a
    Message 1 of 10 , Aug 1, 2010
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      Mike Morris:
      > Hi,
      >
      > I'm working on a mail server deployment that will only have one server
      > for MX and SASL submission purposes. Generally I like to have separate
      > Postfix instances to handle a specific task. In this case I'm running
      > in to problems when the submission instance uses the same IP address as
      > the MX instance. (Due to a limited IP address pool there is currently
      > only one routable IP address assigned to this server.)
      >
      > Using the submission instance to send a message to a recipient address
      > for which the server is also the MX host triggers Postfix' loop
      > detection. Mail for foreign addresses is relayed correctly. I realize
      > this can be done easily enough without using multiple instances. Is
      > there a way to work around this so that an MX instance and submission
      > instance can share single IP address? I've gotten used to the queue,

      If you use different MTAs, then use different myhostname AND
      different inet_interfaces settings. Otherwise it is just too easy
      to screw up and have a high-speed mail system meltdown/explosion/etc.

      Postfix is not just about "secure" for some vague definition of
      secure, it is about making a safe to use, so that it does not rip
      off your arms and legs when you make a trivial mistake.

      Wietse
    • Mike Morris
      ... I don t believe it is totally useless to use separate instances for distinct services. Configurations can get complex. Outgoing mail may be handled
      Message 2 of 10 , Aug 1, 2010
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        On 08/01/2010 02:37 AM, Jeroen Geilman wrote:
        > On 08/01/2010 04:11 AM, Mike Morris wrote:
        >> Hi,
        >>
        >> I'm working on a mail server deployment that will only have one server
        >> for MX and SASL submission purposes. Generally I like to have separate
        >> Postfix instances to handle a specific task.
        >
        > Why ?
        > It's totally useless in this case.
        > SMTP runs on port 25, and rejects anything not_invented_here.
        > Submission runs on port 587, and requires SASL.
        > Simple.

        I don't believe it is "totally useless" to use separate instances for
        distinct services. Configurations can get complex. Outgoing mail may
        be handled differently than incoming mail. Using multiple instances can
        simplify the task. While it may not *work* in this case, using multiple
        instances for MX and submission services is far from *useless*.

        >
        >> mail_version = 2.8-20100707
        >>
        >
        > UNSTABLE.
        > sheesh.
        >

        Plenty of people would argue that Postfix experimental releases are
        quite stable. In this case I would like to test and make use of postscreen.
      • Mike Morris
        ... Fair enough. I ll see what can be done about a second IP address. -Mike
        Message 3 of 10 , Aug 1, 2010
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          On 08/01/2010 09:29 AM, Wietse Venema wrote:
          > Mike Morris:
          >> Hi,
          >>
          >> I'm working on a mail server deployment that will only have one server
          >> for MX and SASL submission purposes. Generally I like to have separate
          >> Postfix instances to handle a specific task. In this case I'm running
          >> in to problems when the submission instance uses the same IP address as
          >> the MX instance. (Due to a limited IP address pool there is currently
          >> only one routable IP address assigned to this server.)
          >>
          >> Using the submission instance to send a message to a recipient address
          >> for which the server is also the MX host triggers Postfix' loop
          >> detection. Mail for foreign addresses is relayed correctly. I realize
          >> this can be done easily enough without using multiple instances. Is
          >> there a way to work around this so that an MX instance and submission
          >> instance can share single IP address? I've gotten used to the queue,
          >
          > If you use different MTAs, then use different myhostname AND
          > different inet_interfaces settings. Otherwise it is just too easy
          > to screw up and have a high-speed mail system meltdown/explosion/etc.
          >
          > Postfix is not just about "secure" for some vague definition of
          > secure, it is about making a safe to use, so that it does not rip
          > off your arms and legs when you make a trivial mistake.
          >
          > Wietse


          Fair enough. I'll see what can be done about a second IP address.

          -Mike
        • Wietse Venema
          Mike Morris: [ Charset ISO-8859-1 unsupported, converting... ] ... Or enable the commented-out submission service (port 587) in the default master.cf file.
          Message 4 of 10 , Aug 1, 2010
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            Mike Morris:
            [ Charset ISO-8859-1 unsupported, converting... ]
            > On 08/01/2010 09:29 AM, Wietse Venema wrote:
            > > Mike Morris:
            > >> Hi,
            > >>
            > >> I'm working on a mail server deployment that will only have one server
            > >> for MX and SASL submission purposes. Generally I like to have separate
            > >> Postfix instances to handle a specific task. In this case I'm running
            > >> in to problems when the submission instance uses the same IP address as
            > >> the MX instance. (Due to a limited IP address pool there is currently
            > >> only one routable IP address assigned to this server.)
            > >>
            > >> Using the submission instance to send a message to a recipient address
            > >> for which the server is also the MX host triggers Postfix' loop
            > >> detection. Mail for foreign addresses is relayed correctly. I realize
            > >> this can be done easily enough without using multiple instances. Is
            > >> there a way to work around this so that an MX instance and submission
            > >> instance can share single IP address? I've gotten used to the queue,
            > >
            > > If you use different MTAs, then use different myhostname AND
            > > different inet_interfaces settings. Otherwise it is just too easy
            > > to screw up and have a high-speed mail system meltdown/explosion/etc.
            > >
            > > Postfix is not just about "secure" for some vague definition of
            > > secure, it is about making a safe to use, so that it does not rip
            > > off your arms and legs when you make a trivial mistake.
            > >
            > > Wietse
            >
            >
            > Fair enough. I'll see what can be done about a second IP address.

            Or enable the commented-out submission service (port 587) in the
            default master.cf file. With this, use port 587 for submission,
            and port 25 for final delivery.

            Wietse
          • Jeroen Geilman
            ... Certainly, and postfix supplies its fair share, as I explained above. ... All mail comes in. all mail goes out. ... Instead of using multiple instances of
            Message 5 of 10 , Aug 5, 2010
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              On 08/01/2010 08:42 PM, Mike Morris wrote:
              > On 08/01/2010 02:37 AM, Jeroen Geilman wrote:
              >
              >> On 08/01/2010 04:11 AM, Mike Morris wrote:
              >>
              >>> Hi,
              >>>
              >>> I'm working on a mail server deployment that will only have one server
              >>> for MX and SASL submission purposes. Generally I like to have separate
              >>> Postfix instances to handle a specific task.
              >>>
              >> Why ?
              >> It's totally useless in this case.
              >> SMTP runs on port 25, and rejects anything not_invented_here.
              >> Submission runs on port 587, and requires SASL.
              >> Simple.
              >>
              > I don't believe it is "totally useless" to use separate instances for
              > distinct services.

              Certainly, and postfix supplies its fair share, as I explained above.
              > Configurations can get complex. Outgoing mail may
              > be handled differently than incoming mail.

              All mail comes in. all mail goes out.

              > Using multiple instances can
              > simplify the task. While it may not *work* in this case, using multiple
              > instances for MX and submission services is far from *useless*.
              >
              Instead of using multiple instances of postfix, why not use multiple
              smtpd-listener instances, like we suggest ?
              >>> mail_version = 2.8-20100707
              >>>
              >>>
              >> UNSTABLE.
              >> sheesh.
              >>
              >>
              > Plenty of people would argue that Postfix experimental releases are
              > quite stable. In this case I would like to test and make use of postscreen.
              >

              Yes, postscreen is sexy... I think there are ways to get it to work with
              2.7, if you're prepared to overlay it onto a 2.7 build and fix what
              breaks (if anything breaks, I know of at least one successful deployment).

              J.
            • Mike Morris
              ... I am aware that from the perspective of an MTA, all mail comes in and all mail goes out. However, from the perspective of an organization, there may be
              Message 6 of 10 , Aug 5, 2010
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                On 08/05/2010 11:57 AM, Jeroen Geilman wrote:
                > On 08/01/2010 08:42 PM, Mike Morris wrote:
                >> On 08/01/2010 02:37 AM, Jeroen Geilman wrote:
                >>
                >>> On 08/01/2010 04:11 AM, Mike Morris wrote:
                >>>
                >>>> Hi,
                >>>>
                >>>> I'm working on a mail server deployment that will only have one server
                >>>> for MX and SASL submission purposes. Generally I like to have separate
                >>>> Postfix instances to handle a specific task.
                >>>>
                >>> Why ?
                >>> It's totally useless in this case.
                >>> SMTP runs on port 25, and rejects anything not_invented_here.
                >>> Submission runs on port 587, and requires SASL.
                >>> Simple.
                >>>
                >> I don't believe it is "totally useless" to use separate instances for
                >> distinct services.
                >
                > Certainly, and postfix supplies its fair share, as I explained above.
                >> Configurations can get complex. Outgoing mail may
                >> be handled differently than incoming mail.
                >
                > All mail comes in. all mail goes out.

                I am aware that from the perspective of an MTA, all mail comes in and
                all mail goes out. However, from the perspective of an organization,
                there may be differences between how mail coming in to, and sent from,
                that organization is handled.

                >
                >> Using multiple instances can
                >> simplify the task. While it may not *work* in this case, using multiple
                >> instances for MX and submission services is far from *useless*.
                >>
                > Instead of using multiple instances of postfix, why not use multiple
                > smtpd-listener instances, like we suggest ?

                I've set up mail systems using both approaches. It isn't always
                possible to foresee what may be required in the future. In the long run
                it often is simpler to maintain the configurations of multiple instances
                from the beginning rather than switch to such a setup after maintaining
                a single instance becomes unwieldy.

                I hadn't intended this to become a multiple- vs. single-instance debate.
                Each individual user can decide which approach best suits their
                environment, and when one is preferred over the other.

                Anyhow, in this particular case we were able to configure the server
                with a second IP address.

                >>>> mail_version = 2.8-20100707
                >>>>
                >>>>
                >>> UNSTABLE.
                >>> sheesh.
                >>>
                >>>
                >> Plenty of people would argue that Postfix experimental releases are
                >> quite stable. In this case I would like to test and make use of postscreen.
                >>
                >
                > Yes, postscreen is sexy... I think there are ways to get it to work with
                > 2.7, if you're prepared to overlay it onto a 2.7 build and fix what
                > breaks (if anything breaks, I know of at least one successful deployment).

                I was wondering if this was going to be your response. I find it
                interesting that the person who shouted "UNSTABLE" in response to
                someone using an experimental Postfix release would then suggest such an
                approach. Out of curiosity, what would your reasons be for suggesting
                running postscreen with 2.7 rather than using a 2.8 snapshot? Wouldn't
                similar instability concerns about the latter apply to the former?

                -Mike
              • Jeroen Geilman
                ... That s not exactly what I meant. 2.8 is not out for release yet, and as such I personally would not recommend using it in production systems, as a general
                Message 7 of 10 , Aug 5, 2010
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                  On 08/05/2010 10:15 PM, Mike Morris wrote:
                  > On 08/05/2010 11:57 AM, Jeroen Geilman wrote:
                  >
                  >> On 08/01/2010 08:42 PM, Mike Morris wrote:
                  >>
                  >>> On 08/01/2010 02:37 AM, Jeroen Geilman wrote:
                  >>>
                  >>>
                  >>>> On 08/01/2010 04:11 AM, Mike Morris wrote:
                  >>>>
                  >>>>
                  >>>>> Hi,
                  >>>>>
                  >>>>> I'm working on a mail server deployment that will only have one server
                  >>>>> for MX and SASL submission purposes. Generally I like to have separate
                  >>>>> Postfix instances to handle a specific task.
                  >>>>>
                  >>>>>
                  >>>> Why ?
                  >>>> It's totally useless in this case.
                  >>>> SMTP runs on port 25, and rejects anything not_invented_here.
                  >>>> Submission runs on port 587, and requires SASL.
                  >>>> Simple.
                  >>>>
                  >>>>
                  >>> I don't believe it is "totally useless" to use separate instances for
                  >>> distinct services.
                  >>>
                  >> Certainly, and postfix supplies its fair share, as I explained above.
                  >>
                  >>> Configurations can get complex. Outgoing mail may
                  >>> be handled differently than incoming mail.
                  >>>
                  >> All mail comes in. all mail goes out.
                  >>
                  > I am aware that from the perspective of an MTA, all mail comes in and
                  > all mail goes out. However, from the perspective of an organization,
                  > there may be differences between how mail coming in to, and sent from,
                  > that organization is handled.
                  >
                  >
                  >>
                  >>> Using multiple instances can
                  >>> simplify the task. While it may not *work* in this case, using multiple
                  >>> instances for MX and submission services is far from *useless*.
                  >>>
                  >>>
                  >> Instead of using multiple instances of postfix, why not use multiple
                  >> smtpd-listener instances, like we suggest ?
                  >>
                  > I've set up mail systems using both approaches. It isn't always
                  > possible to foresee what may be required in the future. In the long run
                  > it often is simpler to maintain the configurations of multiple instances
                  > from the beginning rather than switch to such a setup after maintaining
                  > a single instance becomes unwieldy.
                  >
                  > I hadn't intended this to become a multiple- vs. single-instance debate.
                  > Each individual user can decide which approach best suits their
                  > environment, and when one is preferred over the other.
                  >
                  > Anyhow, in this particular case we were able to configure the server
                  > with a second IP address.
                  >
                  >
                  >>>>> mail_version = 2.8-20100707
                  >>>>>
                  >>>>>
                  >>>>>
                  >>>> UNSTABLE.
                  >>>> sheesh.
                  >>>>
                  >>>>
                  >>>>
                  >>> Plenty of people would argue that Postfix experimental releases are
                  >>> quite stable. In this case I would like to test and make use of postscreen.
                  >>>
                  >>>
                  >> Yes, postscreen is sexy... I think there are ways to get it to work with
                  >> 2.7, if you're prepared to overlay it onto a 2.7 build and fix what
                  >> breaks (if anything breaks, I know of at least one successful deployment).
                  >>
                  > I was wondering if this was going to be your response. I find it
                  > interesting that the person who shouted "UNSTABLE" in response to
                  > someone using an experimental Postfix release would then suggest such an
                  > approach. Out of curiosity, what would your reasons be for suggesting
                  > running postscreen with 2.7 rather than using a 2.8 snapshot? Wouldn't
                  > similar instability concerns about the latter apply to the former?
                  >
                  > -Mike
                  >

                  That's not exactly what I meant.
                  2.8 is not out for release yet, and as such I personally would not
                  recommend using it in production systems, as a general rule, since my
                  testing (or that of any generic user) won't be as rigorous as the
                  developers'.

                  I meant to denominate the version as not being release/stable, not the
                  stability of the code as such.

                  However, earlier on the list Wietse commented on having pulled
                  postscreen from 2.7 (not quite ready yet) and others responsed that they
                  could successfully integrate it with 2.7 anyway.
                  So postscreen is a bit of a special case - it was /almost/ in 2.7.

                  But yeah, the shouting thing was a bit over the top.

                  Sry.
                • Wietse Venema
                  ... The difference is that stable release features not change except in case of emergency, so you can upgrade from one stable Postfix version to the next
                  Message 8 of 10 , Aug 6, 2010
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                    Mike Morris:
                    > approach. Out of curiosity, what would your reasons be for suggesting
                    > running postscreen with 2.7 rather than using a 2.8 snapshot? Wouldn't
                    > similar instability concerns about the latter apply to the former?

                    The difference is that stable release features not change except
                    in case of emergency, so you can upgrade from one stable Postfix
                    version to the next without having to reconfigure Postfix. And when
                    features do have to change, there is a great deal of backwards
                    compatibility.

                    The snapshot releases introduce new features, and those can still
                    change in incompatible ways. For example, postscreen is a prototype
                    that I threw together in a few weeks so that I could present some
                    new measurements at a conference. Once this program is finished
                    sites will almost certainly need to update configuration files.

                    Wietse
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