[SLE] Rejecting backscatter mail in postfix

From: Carlos E. R. (robin1.listas_at_tiscali.es)
Date: 11/27/04

  • Next message: Ken Schneider: "Re: [SLE] Replacementsfor Windows Applications"
    Date: Sat, 27 Nov 2004 22:03:43 +0100 (CET)
    To: SLE <suse-linux-e@suse.com>


    I'm receiving certain backscatter mail (ie, mail sent by postmasters,
    consisting of rejecting a mail with possible virus to the claimed
    originator, which in the case of virus, can be faked, and thus are
    possibly innocent). In this case, the bounce I get includes the full viral
    load, which is a nuisance - and no, amavis-new does not detect it.

    The problem is the "from":

      Return-Path: <>
      From: Mail Delivery System <Mailer-Daemon@mx.mixmail.com>

    I understand that the envelope-from is empty (!). See the log excerpt:

      Nov 26 23:57:25 nimrodel fetchmail[14958]: SMTP> MAIL FROM: <> SIZE=33229
      Nov 26 23:57:25 nimrodel fetchmail[14958]: SMTP< 250 Ok
      Nov 26 23:57:25 nimrodel fetchmail[14958]: SMTP> RCPT TO:<cer@localhost>
      Nov 26 23:57:25 nimrodel postfix/smtpd[14970]: 11CBE20C4D: client=localhost[]
      Nov 26 23:57:25 nimrodel fetchmail[14958]: SMTP< 250 Ok
      Nov 26 23:57:25 nimrodel fetchmail[14958]: SMTP> DATA
      Nov 26 23:57:25 nimrodel fetchmail[14958]: SMTP< 354 End data with <CR><LF>.<CR><LF>
      Nov 26 23:57:25 nimrodel postfix/cleanup[14973]: 11CBE20C4D: message-id=<E1CXnY0-0001VL-00@mx.mixmail.com>

    I have this rule in '/etc/postfix/access', which works for many others
    similar emails:

      mailer-daemon@mx.mixmail.com REJECT Blocking backscatter mail from virus scanners

    but it doesn't trigger in this case :-(


    Perhaps the problem could be that postfix is not checking the sender
    address for existence :-?

    That would be:

    smtpd_sender_restrictions = hash:/etc/postfix/access,reject_unknown_sender_domain

    But that would cause a dns check for every mail, I suppose. What about

           Carlos Robinson
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  • Next message: Ken Schneider: "Re: [SLE] Replacementsfor Windows Applications"

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