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281783Re: Dead Destination configuration

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  • DN Singh
    Dec 1, 2011
      Thanks for the suggestion Robert, but how do I find the time for which Postfix will not attempt a delivery after reaching the fail limit? Instead of outsourcing the task to script, and increasing a dependency, it would be better to keep it with Postfix itself, if possible.

      If there aren't any options, I may have to go with the script. Then, I may need some more help...

      DN Singh

      On Thu, Dec 1, 2011 at 1:29 PM, Robert Schetterer <robert@...> wrote:
      Am 01.12.2011 08:35, schrieb DN Singh:
      > Hello Group,
      > I am trying some extra configuration for postfix where it would mark
      > some destinations as undeliverable. I have found that there are some
      > destinations, start deferring the mails (may be greylisting) for a
      > particular period of time (times ranging from 1min to 4hrs), and after
      > the time window is over, they accept mails properly. So, I would like to
      > configure per-destination dead time limit, where Postfix would not
      > attempt any delivery at all to a destination for the mentioned time.
      > I tried configuring backoff-time, but it only comes into picture after
      > first attempt, which will get deferred, during time the destination is
      > differing. Next, I found
      > "default_destination_concurrency_failed_cohort_limit", but I was unable
      > to find to time for which it will remain dead. I know this is transport
      > configurable, so I can configure different time limits for different
      > destinations. This is because, I do not want any delivery attempts
      > during the time when a destination is marked dead.
      > Is this possible? If yes, then how?
      > Thanks.
      > DN Singh

      perhaps put some kind of scripted hold on them
      if they are always the same

      or use ideas from


      Postfix version 2.5 and later:

         In master.cf set up a dedicated clone of the "smtp" transport for
      the problem destination. In the example below we call it "slow".

         In main.cf configure a short delay between deliveries to the same

             transport_maps = hash:/etc/postfix/transport
             slow_destination_rate_delay = 1
             slow_destination_concurrency_failed_cohort_limit = 100

             example.com  slow:

             # service type  private unpriv  chroot  wakeup  maxproc command
             slow      unix     -       -       n       -       -    smtp

      See also the documentation for default_destination_rate_delay.

      This solution forces the Postfix smtp(8) client to wait for
      $slow_destination_rate_delay seconds between deliveries to the same

      IMPORTANT!! The large slow_destination_concurrency_failed_cohort_limit
      value is needed. This prevents Postfix from deferring all mail for the
      same destination after only one connection or handshake error (the
      reason for this is that non-zero slow_destination_rate_delay forces a
      per-destination concurrency of 1).

      Best Regards

      MfG Robert Schetterer


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