Re: [exim] "Mail delivery failed" backscatter is not spam-sc…

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Author: Todd Lyons
Date:  
To: Yves Goergen
CC: exim-users
Subject: Re: [exim] "Mail delivery failed" backscatter is not spam-scanned
I look upon rejecting NDRs with disdain. I understand that you don't
want to receive these bogus ones, but in order to be RFC compliant,
you do need to accept them if they are some semblance of real NDRs.
Instead of rejecting them, redirect them a separate postmaster
mailbox. I'll just use the username "postmaster" for the example
below. It's untested, but it should be able to get you going in the
right direction.

First, create a router to detect these NDRs using all the usual checks
to make sure it's for a valid local domain and user. Order of routers
is important as a delivery is processed first to last, until it finds
one that handles the delivery, so make sure to put it before any other
delivery routers:

ndr_router:
debug_print: "Router: redirect all NDRs"
driver = redirect
domains = +local_domains
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
# any condition checks for user existence here...
sender = ""
directory_transport = ndr_postmaster

Second, create the transport tha twill deliver it.
ndr_postmaster:
driver = appendfile
maildir_format
maildir_use_size_file
maildir_tag = ,S=$message_size
delivery_date_add
envelope_to_add
return_path_add
user = UID_OF_POSTMASTER
group = UID_OF_POSTMASTER


I was in the middle of answering what I think is this same question on
ServerFault when someone (you?) deleted the question and I could no
longer post it :-)

...Todd


On Tue, Apr 15, 2014 at 6:06 AM, Yves Goergen
<nospam.list@???> wrote:
> Hi,
>
> I'm currently receiving large amounts of backscatter spam that basically
> says "Mail delivery failed: ..." in its subject. SpamAssassin is set up and
> rejects a lot of spam, it's just totally useless on these messages. Normally
> all incoming messages get a spam filter info header added, but these
> messages don't even seem to be processed by SpamAssassin. It's as if Exim
> knows better and directly lets those messages pass into my mailbox.
>
> I want to be in control and let SpamAssassin scan and possibly reject all
> messages, including those that look like mail delivery errors. Then I could
> at least add a rule that rejects all messages of that type, even if it's an
> ugly solution, but so is e-mail itself. But that doesn't even work because
> Exim doesn't pass those messages to SpamAssassin.
>
> Is there some kind of exception built-in in Exim or what's wrong here?
>
> This is Exim 4.71 on Ubuntu 10.04. I could append parts of my config if it
> helps, but that's gonna be lengthy and it'll take some time to collect it.
>
> --
> Yves Goergen
> http://unclassified.de
> http://dev.unclassified.de
>
> --
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--
The total budget at all receivers for solving senders' problems is $0.
If you want them to accept your mail and manage it the way you want,
send it the way the spec says to. --John Levine