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[Off-Topic] Handling automatic replies sent to "from" and ignoring the "return envelope"

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  • David Michard
    Hello, I guess this message is off-topic as it is only loosely related to postfix. You may stop reading this now if you are non interested in such topics. ...
    Message 1 of 1 , Mar 31, 2010
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      Hello,

      I guess this message is off-topic as it is only loosely related to postfix.
      You may stop reading this now if you are non interested in such topics.

      -------
      I am responsible for a mailing list with roughly half a million
      subscribers. The flow is outgoing only as we send a newsletter to
      subscribers.
      We implement different techniques to automatically unsubscribe
      old/invalid/overquota email addresses, among which postfix VERP seems
      to work well.
      Our email are emitted from a noreply email address mapped to /dev/null
      as we cannot handle individual replies. Information regarding how to
      contact us is displayed in every email we send (redirect to a web
      form).

      Lastly I have been mapping the noreply@ email address to a real
      mailbox instead to /dev/null. The results are frightening.
      Hundreds of email are sent to the noreply address each day. Some
      subscribers hit "reply" to contact us and I can understand that as
      most of them are not technically savvy.
      The problem is, a lot of replies come from bots / postmasters and so
      on : antispam software (please fill this captcha), or worse delivery
      failure notifications.
      I do not know the applicable RFC by heart but I thought that delivery
      failure notification and other automated replies should be sent to the
      "return envelope" and not to the "From" field. This is how VERP works
      but I now realize that we are missing significant feedback regarding
      the validity of our user base as we do not -and cannot- monitor the
      noreply email address. We cannot automatically monitor it as we do not
      know what kind of email may be sent to the noreply address:
      - either a subscriber replies to us, in which case we should
      autorespond "please use the web form"
      - either an antispam solution asks us to send a confirmation email in
      which case we should consider this as a (hard) bounce
      - either the reply is a delivery failure notification and we should
      consider this as a (hard) bounce
      - either the reply is a temporary failure notification and we should
      consider this as a (soft) bounce

      Therefore we may have email addresses which have been invalid for
      months/years but are not detected by our VERP handling software.

      I am not willing to develop a software to parse the reply looking for
      some magic keywords (such as postmaster, failure...) to do the sorting
      as judging by the diversity of the reply that I see this promises to
      be an impossible task.
      How do mailing-list managers handle this kind of problem using
      postfix? Is there a comprehensive database of keywords which can be
      implemented to differenciate notifications from other type of emails?

      I reckon I am a bit lost on this one :-)
      Regards,
      David.
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