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291355RE: Null sender address in NDR's

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  • James Day
    Feb 14, 2013
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      > > Is there a sensible way to configure postfix to allow these messages
      > > with null sender addresses to be relayed without opening the smart
      > > host up to exploitation?
      > Sending bounces is not "exploitation", but the "smart host" (really
      > submission service) policy is up to the ISP. Ask them.

      I wasn't trying to suggest that sending bounces would be exploitation, rather that allowing *all* messages with a NULL sender to relayed through could potentially be exploited to send spam as <>

      > NO. Bounces MUST be sent with a null sender address. Otherwise, bounces
      > would elicit bounces in return creating mail loops, sometimes exponentially
      > growing, if a message elicits multiple non-delivery reports.

      Yes I know that and have referred to that point below.

      > The solution is to use a relay that permits bounces. Either the ISP relaxes
      > their policies, or a different relay must be found.

      As I feared, thank you for confirming.

      > > And before anyone comments, yes I know this isn't best practice as
      > > NDR's should have null sender addresses to stop loops (bouncing
      > > bounce-backs!).
      > Not "should", MUST. Not "isn't best practice", rather prohibited.
      > --
      > Viktor.

      I understand and agree however in my experience you sometimes have to fudge things so they operate with incorrectly configured systems (against my own wishes!)

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