spam mails using image/gif in multipart/alternative

[Reiner Steib <reinersteib+gmane@imap.cc>]

Hi,

within the last days, I've seen several spam mails on Gmane with such
a MIME structure[1]:

  <* mixed> Re: unaccommodating
  <1.* alternative>
  <1.1.* alternative>
  <1.1.1 text>
  <1.1.2 html>
  <1.2 gif>
  <2 text>

Gnus displays the image/gif part for me, probably also with the
default settings.

I've committed an addition to the doc string (feel free to improve).
Maybe we should even add "image/.*" in the default?

,----[ <f1> v mm-discouraged-alternatives RET ]
| mm-discouraged-alternatives is a variable defined in `mm-decode.el'.
| Its value is nil
| 
| Documentation:
| List of MIME types that are discouraged when viewing multipart/alternative.
| Viewing agents are supposed to view the last possible part of a message,
| as that is supposed to be the richest.  However, users may prefer other
| types instead, and this list says what types are most unwanted.  If,
| for instance, text/html parts are very unwanted, and text/richtext are
| somewhat unwanted, then the value of this variable should be set
| to:
| 
|  ("text/html" "text/richtext")
| 
| Adding "image/.*" might also be useful.  Spammers use it as the
| prefered part of multipart/alternative messages.
| 
| You can customize this variable.
| 
| [back]
`----

I also fixed the custom type: Matching is done with `string-match' in
`mm-preferred-alternative-precedence' so it should be regexp instead
of string.

Bye, Reiner.

[1] <000001c5fc32$17c2e4a0$486ea8c0__328.46739418364$1134072149$gmane$org@corridor>
    <000001c5f776$d20769f0$d424a8c0@surprising>)
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/