Re: [EXIM] Filtering out duplicate messages

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Author: Lee Bradshaw
Date:  
To: Exim-users
Subject: Re: [EXIM] Filtering out duplicate messages
Thanks for the suggestion Philip; it's working well. Sorry about the
"powerful" comment. I now understand that the programs were designed to do
different things.

On Mon, Nov 30, 1998 at 10:17:22AM +0000, Philip Hazel wrote:
> On Sat, 28 Nov 1998, Lee Bradshaw wrote:
>
> > I asked on the debian list because someone asked about procmail and was
> > told to use exim filters because they were better. They are much more
> > readable, but they aren't as powerful as procmail.
>
> Exim filters provide a different (though related) facility to procmail.
> Each provides facilities that the other does not.
>
> As filters are run at directing time, they act in a similar manner to a
> .forward file, but with the possibility of attaching conditions to the
> forwarding. What I mean by this is that a filter can convert one
> incoming address into several new addresses, all on the same message.
> The delivery is then as if the original message were addressed to those
> new recipients (if any one is a duplicate, for example, it gets
> discarded). Using a delivery agent like procmail provides a different
> facility, because it can use the results of running pipes, etc. However,
> from the MTA's point of view, it is *one* delivery down a pipe to the
> agent; if it then wants to forward for several new recipients, it has to
> create a new message and pass it back to the MTA. I'm not saying that
> either of these is "better"; just that they are different.
>
> The use of Exim filter files and procmail is not mutually exclusive. You
> can easily provide both facilities if you want to, and let the users
> choose which they want to use. You can even automate things so that if a
> user has a .procmailrc file, then delivery automatically goes via
> procmail. Use a director something along the lines of
>
> procmail_check:
> driver = localuser
> require_files = $home/.procmailrc
> transport = procmail_transport
> user = $local_part
>
> together with a suitable pipe transport that passes the message to 
> procmail. The above director should go *before* the localuser director 
> that sets up the remaining deliveries.    

>
>
> -- 
> Philip Hazel            University of Cambridge Computing Service,
> ph10@???      Cambridge, England. Phone: +44 1223 334714.

>


-- 
Lee Bradshaw                 lee@??? (preferred)
Alantro Communications       lee@???


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