Backscatter IP Blacklist due to NDRs

Discussion in 'Mail Gateway: Installation and configuration' started by symmcom, Jul 17, 2019.

  1. symmcom

    symmcom Well-Known Member

    Oct 28, 2012
    Likes Received:

    The PMG is trying to send out lots of Bounce reports to bogus destination we are receiving SPAM emails from. This is putting our IP address into Backscatter IP Blacklist and causing some issue when users are trying to send out emails. Some destination servers rejecting emails coming out from the PMG.

    One way to stop this is by disabling Bounce reports. I really dont want to do that since that will also apply to legit emails trying to come to us. Even if i wanted to do that where is that option in PMG?

    Whats backscatter score should be for this and how to better protect PMG from this sort of things?
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  2. dietmar

    dietmar Proxmox Staff Member
    Staff Member

    Apr 28, 2005
    Likes Received:
    Those report are required by the SMTP protocol, so IMHO it would be a bad idea to disable them...

    I guess you could do it by modifying postfix master,cf bounce service, but that is highly discouraged
    and I never really tried that.
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  3. heutger

    heutger Active Member

    Apr 25, 2018
    Likes Received:
    You should check, why your system is sending bounce reports. Usually (and that's the reason why they are seen as backscattering and you're blacklisted therefor) that should not occur. Your server should verify recipients already on connection and reject connection, if the recipient is not available. So check first, which setting let bounces coming up and try to resolve this instead of disabling them.
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