Re: nnml splitting on encoded headers

[Mark Thomas <swoon@bellatlantic.net>]

On Tue, 28 May 2002, ndw@nwalsh.com wrote:

> Looking at some representative asian spam on my machine, C-u g
> doesn't display the encoding in the subject, instead I see things
> like this:
> 
>   Message-Id: <200205281859.OAA05629@nexus.berkshire.net>
>   Reply-To: no@kojein.com
>   From: ¿¹½º¸Ç<yes@kojein.com>
>   To: ndw@nwalsh.com
>   Subject: (±¸ÀÎ,±¤°í)ÀçÅþ˹٠ÇϽǺР
>   Mime-Version: 1.0
>   Content-Type: text/html; charset="ks_c_5601-1987"

For this particular message, I would use rules:
    ("mail.spam.asian"     "^content-type:.*\\beuc-kr\\b")
    ("mail.spam.asian"     "^content-type:.*\\bks_c_5601-1987\\b")
Edit as necessary to make those fancy-rules.  Luckily there was a
charset in the headers for those split rules to match.

Sometimes I get spam where the Content-Type is multipart/alternative
and there is no charset listed in the headers.  For these, I use the
following rule to catch un-encoded spam:
    ("mail.spam.asian"     "^subject:.*[¡-ÿ]\\{4,\\}")
I figure any mail with more than four high-bit characters in a row in
the subject is probably not one I'm going to be able to read.

I've tried to use the rules
    ("mail.spam.asian"     "^subject:.*=\\?euc-kr\\?")
    ("mail.spam.asian"     "^subject:.*=\\?ks_c_5601-1987\\?")
to catch properly encoded headers, but Gnus decodes the message's
headers before it looks at the split rules (at least for back ends that
use nnmail-article-group) so these rules will never match.

Re-encoding the headers with
   (add-hook 'nnmail-split-hook 'rfc2047-encode-message-header)
lets those rules work.  However, this hook also encodes the previously
unencoded headers, so my match on high-bit-characters no longer works.
Sigh.

The number of unencoded Subject headers I receive far outnumber the
encoded ones, so I removed the function from the nnmail-split-hook.
This will work until I get too many properly encoded spams, in which
case I'll just yank the decoding call out of nnmail-article-group.

-Mark