Re: [Exim] String expansion in filters

On Sun, 11 Apr 2004, David Woodhouse wrote:

> The machine attempting to deliver mail on behalf of a _legitimate_
> sender will generate a bounce. The bounce will, if the machine in
> question isn't behaving particularly stupidly, include your explanatory
> text.
>
> On the other hand, if it's a spammer or a virus sending the offending
> message then they _won't_ generate a bounce; they'll just move on to the
> next victim.

Right, but there's also a third class: a bona fide relay or forwarding
host which has inadvertently/misguidedly accepted an abusive mail and
is now trying to deliver it, with its original (faked) envelope-sender
- if the target host rejects it, then it -will- result in the
intermediate host generating a bounce to the faked sender.

We see quite a proportion of this, due to folks who hold accounts on
"lifelong" alumni mailing list servers and the like.

I don't have any practical solution to the problem; and I sure don't
want to start silently accepting mails, rating them as spam and
dropping them into a black hole in order to avoid generating such
abusive bounces. As far as I am concerned, the responsibility lies
with the intermediate host for having accepted the mail in the first
place, and any inappropriate bounces will be issued on their
authority, not mine, when my server refuses their relayed spam.

But when discussing the consequences of SMTP-time rejection, I think
it's only fair to mention that this is one of the possibilities.

best regards