Re: [Exim] Using lists as OR expressions to make an effectiv…

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Author: Philip Hazel
Date:  
To: Marc Perkel
CC: Exim Users
Subject: Re: [Exim] Using lists as OR expressions to make an effective spam filter
On Sun, 25 May 2003, Marc Perkel wrote:

> I again request that EXIM build this in.


1. What exactly do you want built in? Is it the ability to say "If x
matches any regex in this file"? That ability is already there:

if ${lookup{x}wildlsearch{/some/file}{yes}{no}} is yes then ...

2. Doing a large number of regular expression matches is going to be
inefficient; it will be worth your while to study Jeff Friedl's book in
order to tune your regexes for maximum efficiency.

3. Doing this from within the Exim filter language, which is interpreted
in a simple-minded way (it was never designed for this) is going to be
extremely inefficient. OK, if your load is low and your hosts can handle
the workload, then why not? But if the load increases... I am still of
the opinion that the best place (from an efficiency point of view) to do
this kind of work is in an external program.

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book