Negative look ahead with capturing using pcre

Erik Nørgaard norgaard at
Wed Apr 5 19:31:54 UTC 2006


I am trying to write some rules for filtering email with postfix header
rules. In particular, I'd like to discard anything in a character set I
don't understand, or rather accept ascii, iso-8859-* and utf-8.

So I have created the following rule for mime header checks:

    WARN   MHD1000 Invalid charset: "$1". Use UTF-8 or ISO-8859-X

I have two problems:

First: This rule catches a lot of legitimate mail, ascii or iso
character sets

Secondly: I'd like to catch the character set that is rejected so I can
adjust it if legitimate mail gets blocked. In the above I don't allow
windows-1252 for example.

So, how do I do negative look ahead with capturing using pcre?

Thanks, Erik

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