Re: [Exim] Preventing a bounce conditionally

On Sat, 25 Oct 2003, Philip Hazel wrote:

> You can detect bounces in routers (check for an empty sender). You can
> detect that the message originated locally (check for empty sender host
> address). So if you can detect that this is a bounce of spam (perhaps by
> looking at the headers in the returned message)
[...]

Indeed: there's a few common patterns of "collateral spam"
(non-delivery reports for spam which was sent with a counterfeited
sender address belonging to our domain) which we detect in the DATA
ACL, for example by inspecting the headers for certain patterns, as
you say.

> you can set up a router that throws such messages away.

But we don't just silently discard them: we refuse to accept them.

That's permissible, isn't it? It's then left to the offering MTA as
to what they do about the situation (probably ignore it, but that's
not my problem, AIUI).

Just occasionally some crummy MTA will try to send us a non-delivery
report addressed to MAILER-DAEMON to try and tell us we refused their
non-delivery report, but we break that loop alright.

all the best