Customizing coding priority

[Sven Bretfeld <sven.bretfeld@relwi.unibe.ch>]

Dear List

How can I change the coding priority list? With my
language-environment set to utf-8 the command M-x
describe-coding-system (default, current choices) gives:

Priority order for recognizing coding systems when reading files:
  1. mule-utf-8 (alias: utf-8)
  2. iso-latin-1 (alias: iso-8859-1 latin-1)
  3. iso-2022-jp (alias: junet)
  4. iso-2022-7bit 
  5. iso-2022-7bit-lock (alias: iso-2022-int-1)
  6. iso-2022-8bit-ss2 
  7. emacs-mule 
  8. raw-text 
  9. japanese-shift-jis (alias: shift_jis sjis)
  10. chinese-big5 (alias: big5 cn-big5)
  11. no-conversion (alias: binary)

The problem is that vm doesn't recognize Mails written in iso-8859-15
correctly and therefore encodes my replies in iso-2022-jp instead. 

I think that the problem could be solved if I tell Emacs to use
iso-8859-15 as 3rd priority for recognizing the coding system of
files/mails. 

I have tried adding:

'(set-coding-priority-list '((utf-8) (iso-8859-1) (iso-8859-15)))

to the custom-set-variables. But that doesn't change anything.

Can anybody help me?

Thanks very much
Sven