[Exim] Adding header from external programs (was Re: Detecti…

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Author: Matthew Astley
Date:  
To: exim-users
Subject: [Exim] Adding header from external programs (was Re: Detecting open relays in Received path)
Paul Makepeace wrote:

> From: <michael@???>


> > I second that: Don't block mails from hosts listed in ORBS. Many people
> > will yell at you otherwise.


Adding warning headers is always good, but I'm having problems with this
in exim.

> So, if anyone has any suggestions on actual solutions for detecting messages
> that have passed through an open relay upstream I would be interested to hear
> if only for the fun of having solved that particular problem. I've
> investigated pulling out IP addresses from Received: and then using perl's
> Net::DNS::Resolver to check them but it feels ultra-heavyweight and isn't

[...]

I took some perl from Paul Crowley's site and hacked it for extra
flexibility. My version is easier to use if you have several smarthosts
but it still isn't very useful for a whole system. (You'll need the Mail
and Net::DNS packages for Perl, amongst others)

http://www.hedonism.demon.co.uk/paul/download/index.html
http://www.fruitcake.demon.co.uk

What I'd really like is a system-wide filter that adds warning headers
where entries are found on one of the RBL-alikes, so the lookups only
have to be done once per mail and the users can do further filtering in
their MUA. Problem is that the header to be added has to be hard-coded
in the filter file AFAICS...

I would use a pipe transport but I'd rather not send the entire body
text through perl, especially on this rather slow machine. What would be
really nice is a way of sending just the headers from several messages
through one external process . This would save on compile time for perl
and perhaps allow other optimisations.

I haven't finished investigating the options but if someone fancies
taking the ball and running with it that's fine by me!


Matthew #8-)